Middle School Science Quiz: Gravity Is Attractive
20 questions · exam conditions
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Gravity Is AttractiveQuestion 1 of 20

A class is comparing forces. They notice that electric forces can attract or repel depending on charge, and magnetic forces can attract or repel depending on pole direction. Which statement best describes how gravity differs from electric and magnetic forces based on observations like falling objects, orbits, and tides?

Gravity can repel at long distances, but it attracts at short distances.
Gravity depends on whether an object is metal or plastic, so it can attract or repel depending on the material.
Gravity only attracts: masses pull on each other (falling objects, stable orbits, tides), and no gravitational repulsion has been observed.
Gravity is the same as electric force: like masses repel and opposite masses attract.
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Middle School Science Quiz

Middle School Science Quiz: Gravity Is Attractive

Practice Gravity Is Attractive in Middle School Science with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Gravity Is Attractive, giving you a quick way to practice the rules, question types, and explanations that matter most for Middle School Science.

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Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

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Question 1

A class is comparing forces. They notice that electric forces can attract or repel depending on charge, and magnetic forces can attract or repel depending on pole direction. Which statement best describes how gravity differs from electric and magnetic forces based on observations like falling objects, orbits, and tides?

  1. Gravity can repel at long distances, but it attracts at short distances.
  2. Gravity depends on whether an object is metal or plastic, so it can attract or repel depending on the material.
  3. Gravity only attracts: masses pull on each other (falling objects, stable orbits, tides), and no gravitational repulsion has been observed. (correct answer)
  4. Gravity is the same as electric force: like masses repel and opposite masses attract.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Unlike electric forces (where like charges repel: two positive charges push apart, two negative charges push apart) and magnetic forces (where like poles repel: north-north repel, south-south repel), gravitational forces have no repulsive configuration—you cannot arrange masses to make them repel each other the way you can arrange charges (both positive) or magnets (both north poles facing) to create repulsion. Choice C is correct because it accurately explains that gravity differs from electric/magnetic by being only attractive. Choice A incorrectly claims gravitational repulsion exists or has been observed, when actually no gravitational repulsion has ever been detected in any experiment or observation. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces.

Question 2

Which piece of evidence best connects tides to the idea that gravity is attractive (pulling) rather than repulsive (pushing)?

  1. Tides happen because ocean water is pushed away from the Moon by the Moon's gravity.
  2. Tides happen because the Moon's gravity pulls on Earth's oceans, creating a bulge of water toward the Moon. (correct answer)
  3. Tides happen because wind pushes water across the ocean.
  4. Tides happen because Earth's magnetic field repels ocean water.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Every single observation of gravitational force shows attraction: when you drop a book, it falls down toward Earth (Earth's gravity attracts the book), never up or sideways (no gravitational repulsion pushing it away); the Moon stays in orbit around Earth because Earth's gravity continuously pulls it inward (if gravity repelled at some distances or configurations, the Moon would spiral away, but it doesn't—it's held in orbit by attractive force); and ocean tides are high on the side facing the Moon because the Moon's gravity attracts the water creating a bulge (if gravity repelled, water would bulge away from Moon on opposite side only, but actually it bulges toward Moon showing attraction). Choice B is correct because it properly cites evidence showing only attraction: falling, orbits, tides all demonstrate gravitational attraction. Choice A uses evidence that actually shows attraction (falling toward Earth) but misinterprets it as repulsion. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 3

Which observation about tides best supports the idea that gravity is attractive?

Think about what the Moon's gravity does to Earth's oceans.

  1. Tides happen because the Moon's gravity pushes ocean water away from the Moon.
  2. Tides happen because Earth's rotation creates electric charges in the ocean that repel the Moon.
  3. Tides happen because the Moon's gravity pulls on Earth's oceans, creating a bulge toward the Moon. (correct answer)
  4. Tides prove gravity can both attract and repel depending on the time of day.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. For observational evidence: Every single observation of gravitational force shows attraction: when you drop a book, it falls down toward Earth (Earth's gravity attracts the book), never up or sideways (no gravitational repulsion pushing it away); the Moon stays in orbit around Earth because Earth's gravity continuously pulls it inward (if gravity repelled at some distances or configurations, the Moon would spiral away, but it doesn't—it's held in orbit by attractive force); and ocean tides are high on the side facing the Moon because the Moon's gravity attracts the water creating a bulge (if gravity repelled, water would bulge away from Moon on opposite side only, but actually it bulges toward Moon showing attraction). Choice C is correct because it properly cites evidence showing only attraction: tides demonstrate gravitational attraction. Choice A is incorrect because it uses evidence that actually shows attraction (tides) but misinterprets it as repulsion. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 4

Which set of observations provides the strongest evidence that gravity is always attractive (never repulsive)?

  1. Like charges repel; unlike charges attract; magnets can repel.
  2. Books fall toward Earth when dropped, the Moon stays in orbit around Earth, and ocean tides occur because the Moon pulls on Earth's water. (correct answer)
  3. A compass needle points north, and magnets stick to refrigerators.
  4. Some objects float in water while others sink.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Every single observation of gravitational force shows attraction: when you drop a book, it falls down toward Earth (Earth's gravity attracts the book), never up or sideways (no gravitational repulsion pushing it away); the Moon stays in orbit around Earth because Earth's gravity continuously pulls it inward (if gravity repelled at some distances or configurations, the Moon would spiral away, but it doesn't—it's held in orbit by attractive force); and ocean tides are high on the side facing the Moon because the Moon's gravity attracts the water creating a bulge (if gravity repelled, water would bulge away from Moon on opposite side only, but actually it bulges toward Moon showing attraction). Choice B is correct because it provides multiple clear examples of gravitational attraction: falling books show Earth attracts objects, the Moon's orbit shows Earth attracts the Moon, and tides show the Moon attracts Earth's water—all demonstrating gravity only pulls, never pushes. Choice A describes electric and magnetic behavior (repulsion between like charges/poles), not gravitational observations, and actually highlights how gravity differs from these forces by never showing repulsion. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) we can rely on gravity consistently for everything from walking on Earth to planning space missions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces.

Question 5

A student claims, "Gravity is always attractive—it only pulls objects together and never pushes them apart." Which set of observations best supports this claim?

Consider everyday evidence (like objects falling), space evidence (like orbits), and Earth evidence (like tides).​

  1. Astronauts float in space, so gravity must be pushing them away from Earth.
  2. Books fall to the floor, the Moon stays in orbit around Earth, and ocean tides happen because the Moon pulls on Earth's water. (correct answer)
  3. Magnets can repel each other, so gravity can repel too.
  4. Planets orbit the Sun because the Sun's gravity repels them and keeps them from crashing into it.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. This universal attraction occurs because mass (the source of gravity) only comes in one type (positive), unlike electric charge (can be + or -) or magnetic poles (can be N or S), so there's no 'like repels like' for gravity the way there is for charges (++ repel) or magnets (NN repel). Choice B is correct because it properly cites evidence showing only attraction: falling books, Moon's orbit, and tides all demonstrate gravitational attraction. Choice A is incorrect because it cites weightlessness in space as evidence of repulsion, when actually astronauts still experience gravitational attraction (they're in free-fall orbit, continuously falling toward Earth, not being pushed away). The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 6

Which statement is most consistent with Newton's idea that "every mass attracts every other mass" and with what we observe in nature (falling objects, orbits, and tides)?

  1. Gravity can repel if two objects are made of the same material.
  2. Gravity only works between very large objects like planets, not between smaller objects.
  3. All objects with mass attract each other; the attraction may be tiny for small masses, and no gravitational repulsion has been observed. (correct answer)
  4. Gravity is mostly repulsive, but air resistance hides the effect near Earth.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. For universal attraction: Gravitational attraction is truly universal: large masses attract each other (planets, stars, galaxies all pull together forming solar systems, galaxies, galaxy clusters), small masses attract each other (you and this book attract each other gravitationally, though force is imperceptibly tiny), different materials all attract (rock attracts rock, water attracts iron, everything attracts everything else), and there are no exceptions—no materials, no configurations, no conditions where gravity repels, which strongly supports the claim that gravity is always and only attractive. Choice C is correct because it recognizes that all observations support attraction-only claim. Choice A is incorrect because it incorrectly claims gravitational repulsion exists or has been observed, when actually no gravitational repulsion has ever been detected in any experiment or observation. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 7

A student says, "If gravity could repel, planets would still orbit the Sun the same way." Which response best uses evidence from orbits to evaluate that claim?

  1. Orbits show attraction: the Sun's gravity pulls planets inward; if gravity repelled, planets would tend to be pushed away and fly off rather than stay bound. (correct answer)
  2. Orbits prove gravity is repulsive because planets do not crash into the Sun.
  3. Orbits happen only because planets have engines that keep them circling, not because of gravity.
  4. Orbits show gravity changes from attraction to repulsion every half turn around the Sun.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. For observational evidence: Every single observation of gravitational force shows attraction: when you drop a book, it falls down toward Earth (Earth's gravity attracts the book), never up or sideways (no gravitational repulsion pushing it away); the Moon stays in orbit around Earth because Earth's gravity continuously pulls it inward (if gravity repelled at some distances or configurations, the Moon would spiral away, but it doesn't—it's held in orbit by attractive force); and ocean tides are high on the side facing the Moon because the Moon's gravity attracts the water creating a bulge (if gravity repelled, water would bulge away from Moon on opposite side only, but actually it bulges toward Moon showing attraction). Choice A is correct because it properly cites evidence showing only attraction: orbits demonstrate gravitational attraction. Choice B is incorrect because it incorrectly claims gravitational repulsion exists or has been observed, when actually no gravitational repulsion has ever been detected in any experiment or observation. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 8

Which statement correctly compares gravity to electric and magnetic forces?

Electric forces can attract or repel depending on charge (+/−). Magnetic forces can attract or repel depending on pole (N/S).

  1. Gravity can repel when two objects have the same kind of mass, like two positive charges repelling.
  2. Gravity is sometimes attractive and sometimes repulsive depending on distance, but electric forces are always attractive.
  3. Gravity only attracts (pulls masses together), while electric and magnetic forces can either attract or repel. (correct answer)
  4. Gravity and magnetism are the same force, so both must repel in some situations.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. This universal attraction occurs because mass (the source of gravity) only comes in one type (positive), unlike electric charge (can be + or -) or magnetic poles (can be N or S), so there's no 'like repels like' for gravity the way there is for charges (++ repel) or magnets (NN repel). Choice C is correct because it accurately explains that gravity differs from electric/magnetic by being only attractive. Choice A is incorrect because it suggests gravitational repulsion exists or has been observed, when actually no gravitational repulsion has ever been detected in any experiment or observation. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 9

Which statement is most consistent with Newton's idea that "every mass attracts every other mass" and with what we observe in nature (falling objects, orbits, and tides)?​

  1. Gravity can repel if two objects are made of the same material.
  2. Gravity only works between very large objects like planets, not between smaller objects.
  3. All objects with mass attract each other; the attraction may be tiny for small masses, and no gravitational repulsion has been observed. (correct answer)
  4. Gravity is mostly repulsive, but air resistance hides the effect near Earth.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. For universal attraction: Gravitational attraction is truly universal: large masses attract each other (planets, stars, galaxies all pull together forming solar systems, galaxies, galaxy clusters), small masses attract each other (you and this book attract each other gravitationally, though force is imperceptibly tiny), different materials all attract (rock attracts rock, water attracts iron, everything attracts everything else), and there are no exceptions—no materials, no configurations, no conditions where gravity repels, which strongly supports the claim that gravity is always and only attractive. Choice C is correct because it recognizes that all observations support attraction-only claim. Choice A is incorrect because it incorrectly claims gravitational repulsion exists or has been observed, when actually no gravitational repulsion has ever been detected in any experiment or observation. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 10

Two students discuss forces:

Student 1: "Like electric charges repel, so maybe like masses repel too." Student 2: "But we don't see that."

Which statement best supports Student 2 using observations?​

  1. Two massive objects (like Earth and the Moon) stay gravitationally bound, and dropped objects fall toward Earth—both show attraction between masses. (correct answer)
  2. Two north poles of magnets repel, so two masses must repel.
  3. When you rub a balloon on hair, it can repel another balloon, so gravity must also repel sometimes.
  4. Objects fall because air pushes them down, not because of gravity.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. For universal attraction: Gravitational attraction is truly universal: large masses attract each other (planets, stars, galaxies all pull together forming solar systems, galaxies, galaxy clusters), small masses attract each other (you and this book attract each other gravitationally, though force is imperceptibly tiny), different materials all attract (rock attracts rock, water attracts iron, everything attracts everything else), and there are no exceptions—no materials, no configurations, no conditions where gravity repels, which strongly supports the claim that gravity is always and only attractive. Choice A is correct because it properly cites evidence showing only attraction: falling objects and orbits demonstrate gravitational attraction. Choice B is incorrect because it confuses other forces with gravity: uses example of magnetic repulsion claiming it's gravitational. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 11

Ocean tides happen because the Moon's gravity pulls on Earth's oceans, creating bulges of water. Which statement best explains how tides support the idea that gravity is only attractive?

  1. Tides show gravity can both pull water toward the Moon and push water away from the Moon.
  2. Tides show the Moon's gravity attracts ocean water; we do not observe the Moon's gravity pushing ocean water away as a repulsive force. (correct answer)
  3. Tides are caused by Earth's magnetic field repelling ocean water.
  4. Tides prove gravity depends on whether an object is metal or not.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Ocean tides provide clear evidence of gravitational attraction: the Moon's gravity pulls on Earth's oceans, creating a bulge of water on the side facing the Moon (and a corresponding bulge on the opposite side due to Earth being pulled away from the water), but we never observe the Moon's gravity pushing water away as would happen if gravity could repel. Choice B is correct because it accurately explains that tides show the Moon's gravity attracts ocean water, and we do not observe any repulsive gravitational force pushing water away from the Moon. Choice A incorrectly claims tides show gravity can both pull and push water, when actually both tidal bulges result from attractive forces (one from direct pull, one from differential pull on Earth vs water), not from any repulsive gravity. The always-attractive nature of gravity has profound implications: (1) tides are predictable because gravity consistently attracts—if gravity could randomly repel, tides would be chaotic, (2) understanding tides as purely attractive helps us predict ocean behavior for navigation and coastal planning. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces.

Question 12

A student drops a book, a pencil, and a tennis ball from the same height. All three objects move downward toward Earth, and none of them are pushed away from Earth. Which statement best supports the claim that gravity is always attractive (only pulls, never pushes)?

  1. Gravity sometimes pushes objects upward, but air resistance hides it.
  2. Because different objects fall, gravity must sometimes repel light objects.
  3. Objects released near Earth fall toward Earth, showing Earth's gravity pulls objects inward rather than pushing them away. (correct answer)
  4. Objects fall because magnetism pulls them down to the ground.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. The student's observation that all three objects (book, pencil, tennis ball) fall downward toward Earth provides direct evidence of gravitational attraction: Earth's gravity pulls each object toward Earth's center, regardless of the object's material, shape, or mass, demonstrating that gravity consistently attracts rather than repels. Choice C is correct because it properly cites evidence showing only attraction: the downward motion of all dropped objects demonstrates Earth's gravitational pull, with no objects being pushed away from Earth. Choice A incorrectly claims gravitational repulsion exists but is hidden by air resistance, when actually no gravitational repulsion has ever been detected in any experiment or observation, even in vacuum chambers where air resistance is eliminated. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth). If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces.

Question 13

A student claims, "Gravity is always attractive—it only pulls objects together and never pushes them apart." Which set of observations best supports this claim?

Consider everyday evidence (like objects falling), space evidence (like orbits), and Earth evidence (like tides).

  1. Astronauts float in space, so gravity must be pushing them away from Earth.
  2. Books fall to the floor, the Moon stays in orbit around Earth, and ocean tides happen because the Moon pulls on Earth's water. (correct answer)
  3. Magnets can repel each other, so gravity can repel too.
  4. Planets orbit the Sun because the Sun's gravity repels them and keeps them from crashing into it.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. This universal attraction occurs because mass (the source of gravity) only comes in one type (positive), unlike electric charge (can be + or -) or magnetic poles (can be N or S), so there's no 'like repels like' for gravity the way there is for charges (++ repel) or magnets (NN repel). Choice B is correct because it properly cites evidence showing only attraction: falling books, Moon's orbit, and tides all demonstrate gravitational attraction. Choice A is incorrect because it cites weightlessness in space as evidence of repulsion, when actually astronauts still experience gravitational attraction (they're in free-fall orbit, continuously falling toward Earth, not being pushed away). The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.

Question 14

Which statement best summarizes the evidence from many observations (falling objects, orbits, and tides) about whether gravity can repel?

  1. There are many clear observations of gravity pushing objects apart, especially in orbits.
  2. Gravity sometimes attracts and sometimes repels, depending on the material of the object.
  3. Across many observations, gravity is always seen pulling masses together, and no reliable observation shows gravitational repulsion. (correct answer)
  4. Gravity repels small objects but attracts large objects.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Gravitational attraction is truly universal: large masses attract each other (planets, stars, galaxies all pull together forming solar systems, galaxies, galaxy clusters), small masses attract each other (you and this book attract each other gravitationally, though force is imperceptibly tiny), different materials all attract (rock attracts rock, water attracts iron, everything attracts everything else), and there are no exceptions—no materials, no configurations, no conditions where gravity repels, which strongly supports the claim that gravity is always and only attractive. Choice C is correct because it accurately summarizes the overwhelming evidence: across many observations including falling objects (always fall down, never up), orbits (objects held in curved paths by inward pull, not pushed away), and tides (water pulled toward Moon, not pushed away), gravity is always seen pulling masses together with no reliable observation ever showing gravitational repulsion. Choice A falsely claims there are many observations of gravity pushing objects apart, particularly in orbits, when actually orbits demonstrate attraction (inward pull keeps objects circling rather than flying away). Choice B incorrectly states gravity sometimes repels depending on material, when gravity attracts all materials equally regardless of composition. Choice D wrongly claims gravity repels small objects while attracting large ones, when actually gravity attracts all objects regardless of size (though the force is weaker between smaller masses).

Question 15

Which choice best contrasts gravity with electric force using the ideas of attraction and repulsion?

  1. Gravity can repel if two objects have the same mass, while electric force always attracts.
  2. Gravity always attracts masses, while electric force can attract or repel depending on whether charges are opposite or the same. (correct answer)
  3. Gravity and electric force both repel when objects are far apart.
  4. Gravity only works in space, while electric force only works on Earth.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Unlike electric forces (where like charges repel: two positive charges push apart, two negative charges push apart) and magnetic forces (where like poles repel: north-north repel, south-south repel), gravitational forces have no repulsive configuration—you cannot arrange masses to make them repel each other the way you can arrange charges (both positive) or magnets (both north poles facing) to create repulsion. This fundamental difference exists because mass comes in only one type (all positive, no negative mass), while charge has two types (+/-) and magnets have two pole types (N/S), and it's the existence of opposite types that allows repulsion in electric and magnetic forces but not in gravity. Choice B is correct because it accurately contrasts gravity with electric force: gravity always attracts masses (no repulsion ever), while electric force can attract (opposite charges: + and -) or repel (like charges: ++ or --) depending on charge types. Choice A reverses the facts, incorrectly claiming gravity can repel objects with same mass while electric force always attracts, when actually gravity always attracts and electric force can repel. Choice C wrongly states both forces repel at large distances, when actually both forces weaken with distance but maintain their attractive/repulsive nature. Choice D makes false claims about where each force operates, when both gravity and electric forces work everywhere in the universe.

Question 16

Electric and magnetic forces can either attract or repel. Why is gravity different from these forces in everyday situations?

  1. Gravity can switch between attraction and repulsion depending on distance, like magnets do.
  2. Gravity only affects objects made of metal, so it seems like it always attracts.
  3. Mass is only observed as one "type" (no negative mass has been observed), so gravity always pulls masses together rather than sometimes pushing them apart. (correct answer)
  4. Gravity is the same as electric force because both use positive and negative mass.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Unlike electric forces (where like charges repel: two positive charges push apart, two negative charges push apart) and magnetic forces (where like poles repel: north-north repel, south-south repel), gravitational forces have no repulsive configuration—you cannot arrange masses to make them repel each other the way you can arrange charges (both positive) or magnets (both north poles facing) to create repulsion. This fundamental difference exists because mass comes in only one type (all positive, no negative mass), while charge has two types (+/-) and magnets have two pole types (N/S), and it's the existence of opposite types that allows repulsion in electric and magnetic forces but not in gravity. Choice C is correct because it accurately explains that gravity differs from electric/magnetic forces by being only attractive: mass only comes in one type (positive), so there's no "like repels like" scenario as with electric charges or magnetic poles. Choice A incorrectly claims gravity can switch between attraction and repulsion like magnets do, when actually gravity is always attractive regardless of distance. Choice B wrongly states gravity only affects metal objects, when actually gravity affects all matter regardless of composition. Choice D confuses fundamental concepts by claiming gravity uses "positive and negative mass" like electric force uses charge, but negative mass has never been observed—all mass is positive, which is why gravity only attracts.

Question 17

Which observation is the best evidence that gravity does not act like electric charge, where "like" can repel?

  1. Two positively charged objects can repel each other.
  2. Two objects with mass (like two rocks) still attract each other gravitationally, even though they are the "same kind" of mass. (correct answer)
  3. A magnet can attract a paper clip.
  4. A charged comb can attract small bits of paper.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Unlike electric forces where like charges repel (two positive charges push apart, two negative charges push apart) and magnetic forces where like poles repel (north-north repel, south-south repel), gravitational forces have no repulsive configuration—you cannot arrange masses to make them repel each other the way you can arrange charges (both positive) or magnets (both north poles facing) to create repulsion. Choice B is correct because it properly demonstrates that gravity doesn't follow the "like repels like" rule of electric charges: two rocks (same kind of mass) still attract each other gravitationally, whereas two positive charges would repel—this shows gravity fundamentally differs from electric force. Choice A describes electric repulsion (two positive charges repelling), which actually demonstrates how electric force works, not how gravity differs from it. Choice C shows magnetic attraction and Choice D shows electric attraction, but neither contrasts gravity's behavior with the repulsion seen in electric/magnetic forces when "like" meets "like." The key insight is that gravity has no configuration where "same" repels "same"—all masses attract all other masses regardless of being the same type, unlike charges or magnetic poles where matching types repel.

Question 18

Which statement is a strong, evidence-based argument that gravity is universally attractive (every mass attracts every other mass)?

  1. Only heavy objects have gravity, so small objects do not attract anything.
  2. Gravity is attractive on Earth but repulsive on other planets.
  3. From small scales (dropping a coin) to large scales (the Moon orbiting Earth and planets orbiting the Sun), gravity always pulls masses toward each other, and no gravitational repulsion has been observed anywhere. (correct answer)
  4. Gravity is caused by Earth's magnetism, which can attract or repel.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. This universal attraction occurs because mass (the source of gravity) only comes in one type (positive), unlike electric charge (can be + or -) or magnetic poles (can be N or S), so there's no 'like repels like' for gravity the way there is for charges (++ repel) or magnets (NN repel). For universal attraction: Gravitational attraction is truly universal: large masses attract each other (planets, stars, galaxies all pull together forming solar systems, galaxies, galaxy clusters), small masses attract each other (you and this book attract each other gravitationally, though force is imperceptibly tiny), different materials all attract (rock attracts rock, water attracts iron, everything attracts everything else), and there are no exceptions—no materials, no configurations, no conditions where gravity repels, which strongly supports the claim that gravity is always and only attractive. Choice C is correct because it correctly constructs argument using multiple evidence pieces all showing attraction with no repulsion. Choice A incorrectly claims gravitational repulsion exists or has been observed, when actually no gravitational repulsion has ever been detected in any experiment or observation. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions.

Question 19

A student says, "Astronauts float in the International Space Station because Earth's gravity is pushing them away." Which response uses evidence to show this claim is incorrect and that gravity is attractive?

  1. Astronauts float because gravity is stronger in space than on Earth.
  2. Astronauts float because there is no gravity in space at all.
  3. Astronauts float because the station and astronauts are falling around Earth together; Earth's gravity is still pulling them toward Earth, not pushing them away. (correct answer)
  4. Astronauts float because Earth's magnetic field repels them upward.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. Astronauts float in the International Space Station not because gravity is absent or repelling them, but because both the station and astronauts are in free fall—they're continuously falling toward Earth together, but their sideways motion keeps them in orbit, so Earth's gravity is still attracting them (pulling them toward Earth's center), not pushing them away. Choice C is correct because it properly explains that astronauts float due to being in free fall with their spacecraft, while Earth's gravity continues to pull them toward Earth (attractive force), directly refuting the claim that gravity is pushing them away. Choice B incorrectly claims there is no gravity in space, when actually Earth's gravity at the ISS altitude (about 400 km) is still about 90% as strong as at Earth's surface—astronauts are definitely experiencing gravitational attraction. The always-attractive nature of gravity has profound implications: (1) satellites and space stations stay in orbit because gravity continuously pulls them toward Earth (if gravity repelled, they'd fly away into deep space), (2) understanding weightlessness as free fall rather than absence of gravity helps design spacecraft and train astronauts. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction, including all spacecraft missions which rely on gravitational attraction for orbits and trajectory planning.

Question 20

Two students discuss forces:

Student 1: "Like electric charges repel, so maybe like masses repel too." Student 2: "But we don't see that."

Which statement best supports Student 2 using observations?

  1. Two massive objects (like Earth and the Moon) stay gravitationally bound, and dropped objects fall toward Earth—both show attraction between masses. (correct answer)
  2. Two north poles of magnets repel, so two masses must repel.
  3. When you rub a balloon on hair, it can repel another balloon, so gravity must also repel sometimes.
  4. Objects fall because air pushes them down, not because of gravity.
Explanation: This question tests understanding that gravitational forces are always attractive (only pull objects together, never push apart), which distinguishes gravity from electric and magnetic forces that can either attract or repel. The claim that gravitational forces are always attractive is supported by overwhelming evidence: (1) all objects fall downward toward Earth (attracted by gravity) and nothing is ever repelled upward by gravity, (2) all planets orbit their stars because gravity pulls them inward—if gravity could repel, planets would fly away from the Sun instead of orbiting, (3) tides occur because the Moon's gravity attracts Earth's oceans (water bulges toward Moon), not repels them, (4) throughout all of scientific observation and experimentation, no case of gravitational repulsion has ever been found—everything with mass attracts everything else with mass, without exception. For universal attraction: Gravitational attraction is truly universal: large masses attract each other (planets, stars, galaxies all pull together forming solar systems, galaxies, galaxy clusters), small masses attract each other (you and this book attract each other gravitationally, though force is imperceptibly tiny), different materials all attract (rock attracts rock, water attracts iron, everything attracts everything else), and there are no exceptions—no materials, no configurations, no conditions where gravity repels, which strongly supports the claim that gravity is always and only attractive. Choice A is correct because it properly cites evidence showing only attraction: falling objects and orbits demonstrate gravitational attraction. Choice B is incorrect because it confuses other forces with gravity: uses example of magnetic repulsion claiming it's gravitational. The always-attractive nature of gravity has profound implications: (1) gravity pulls all matter together forming structures (planets from dust clouds, stars from gas, galaxies from scattered matter), (2) objects don't fly apart spontaneously due to gravity (only other forces like electrostatic repulsion can cause that), (3) we can rely on gravity consistently (won't suddenly repel and send us flying into space—always pulls us to Earth), and (4) understanding gravity as attractive-only helps distinguish it from electric and magnetic forces in explanations and predictions. If you ever see objects repelling (pushing apart), you know it's not gravity—it's either electric forces (like charges), magnetic forces (like poles), or mechanical forces (compressed spring, air pressure), but never gravitational forces. This certainty comes from the perfect record: in all of human history, every gravitational measurement and observation has shown attraction (literally billions of observations from falling objects to planetary motions to galactic clustering), with zero counterexamples of repulsion—such overwhelming one-sided evidence strongly supports the scientific claim that gravitational forces are always attractive, which is now a fundamental principle in physics that explains phenomena from why we don't float off Earth to how the universe's large-scale structure formed through gravitational attraction pulling matter together over billions of years.