Middle School Science Quiz: Predict Collision Motion

20 questions · exam conditions

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Predict Collision MotionQuestion 1 of 20

Two identical carts (same mass) collide on a straight track. Before the collision, Cart A moves right at $5\,\text{m/s}$ and Cart B is at rest. Assuming a typical nearly elastic cart collision, which prediction is most reasonable for what happens right after the collision?

Cart A keeps moving right at

5\,\text{m/s}

and Cart B stays at rest because Cart A is the only one with momentum.

Cart A slows down or may stop, and Cart B speeds up and moves to the right, because during the collision they push on each other with equal and opposite forces.

Both carts move to the right at

5\,\text{m/s}

because equal masses must end with equal speeds.

Cart B moves left because the force on it must be opposite the direction Cart A was moving.

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Middle School Science Quiz

Middle School Science Quiz: Predict Collision Motion

Practice Predict Collision Motion 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 Predict Collision Motion, giving you a quick way to practice the rules, question types, and explanations that matter most for Middle School Science.

How to use this quiz

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.

All questions

Question 1

Cart A keeps moving right at $5\,\text{m/s}$ and Cart B stays at rest because Cart A is the only one with momentum.
Cart A slows down or may stop, and Cart B speeds up and moves to the right, because during the collision they push on each other with equal and opposite forces. (correct answer)
Both carts move to the right at $5\,\text{m/s}$ because equal masses must end with equal speeds.
Cart B moves left because the force on it must be opposite the direction Cart A was moving.

Question 2

A student jumps straight up from the ground. While pushing off, the student's feet push down on the ground.

Which statement best predicts what happens during the push-off, and why the ground does not noticeably move?

Before: student at rest, ground at rest During: push forces After: student upward motion

The student pushes down on the ground, and the ground pushes up on the student with an equal and opposite force; the ground's acceleration is too small to notice because its mass is enormous ( $a=F/m$ ). (correct answer)
The student pushes down on the ground, but the ground does not push back; the student rises because of the force from their legs only.
The ground pushes up with a larger force than the student pushes down, which is why the student lifts off.
Only the student experiences a force because the ground is not an object that can experience forces.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart like jumping: The student pushes down on the ground, and the ground pushes up on the student—both experience equal opposite forces (Newton's Third Law), so both accelerate (student up, ground down, though ground's change is tiny due to huge mass). The student's motion changes noticeably (jumps up), and the ground's motion changes imperceptibly due to mass difference (same F, large m → small a). Choice A is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / appropriately connects equal forces with different motion changes when masses differ. Choice B is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 3

Two identical bumper cars (same mass) move on a flat surface. Car A moves east at $5\,\text{m/s}$ . Car B is at rest. Car A hits Car B from behind.

What is the best qualitative prediction for the motion of both cars right after the collision?

Car A will slow down a lot (possibly stop) and Car B will move east; both change motion because the cars push on each other with equal and opposite forces. (correct answer)
Only Car B moves because it receives the force; Car A keeps $5\,\text{m/s}$ because it is the one applying the force.
Both cars move west because the equal and opposite forces cancel the eastward motion.
Neither car changes speed because equal masses make the collision forces cancel out.

Question 4

Cart A (mass 2 kg) is moving right at 4 m/s on a low-friction track. Cart B (mass 2 kg) is at rest. They collide and stick together.

Before: A moving right, B at rest. During: each cart pushes on the other with equal and opposite forces. After: Which statement best predicts the motion of BOTH carts after the collision, and why both are affected?

Only Cart B changes motion because Cart A was already moving; Cart A keeps moving right at 4 m/s.
Both carts feel equal and opposite forces, so both change motion; they move together to the right at a speed less than 4 m/s. (correct answer)
Both carts feel forces, but Cart B stays at rest because it started at rest; Cart A slows down a little.
Cart A exerts a larger force on Cart B than Cart B exerts on Cart A, so Cart B moves right while Cart A keeps the same speed.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. When Cart A (moving right at 4 m/s) collides with Cart B (at rest) and they stick together, both carts experience equal magnitude forces during the collision: Cart A experiences force to the left (opposite its motion) causing it to slow down, while Cart B experiences equal force to the right causing it to speed up from rest; since the carts have equal masses and stick, Cart A slows from 4 m/s to 2 m/s, and Cart B speeds up from 0 to 2 m/s, with both moving together right at 2 m/s after (momentum conservation). Choice B is correct because it properly predicts both objects change motion based on both experiencing forces and accurately describes them moving together to the right at a speed less than 4 m/s. Choice A is wrong because it predicts only Cart B changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 5

Two carts collide head-on on a low-friction track.

Before: Cart A (2 kg) moves right at 2 m/s. Cart B (2 kg) moves left at 2 m/s. During: each cart exerts an equal and opposite force on the other.

After the collision, which statement best describes what can happen to BOTH carts' motions?

Both carts must keep moving in their original directions because the forces are equal and cancel out.
Only the cart moving right changes motion; the cart moving left is unaffected because it was "pushing back."
Both carts change motion during the collision; they may slow down and could reverse directions depending on the details of the collision. (correct answer)
Cart A exerts more force because it is labeled A, so Cart B must reverse direction while Cart A keeps the same speed.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. When two equal-mass carts approach each other head-on at equal speeds and collide, both experience equal opposite forces, so both will change motion: they may slow down, stop, or reverse directions depending on whether the collision is elastic (reverse) or inelastic (stop or slow). Choice C is correct because it properly predicts both objects change motion based on both experiencing forces and accurately predicts they may slow down and could reverse directions from the opposite accelerations. Choice A is wrong because it predicts no motion change for either object, when collision forces must cause accelerations by F = ma, and claims forces cancel out overall but ignores that forces act on different objects. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 6

A rocket in space fires its engine and shoots hot gases backward (to the left).

Before: rocket and gases are together. During: rocket pushes gases left; gases push rocket right with equal and opposite force.

Which prediction best describes the motion changes of BOTH the rocket and the gases?

Only the gases accelerate because they are being pushed; the rocket stays at the same speed.
The rocket accelerates right while the gases accelerate left; both change motion due to equal and opposite forces. (correct answer)
Both the rocket and the gases accelerate to the right because the rocket engine points right.
The rocket accelerates right because it exerts a larger force on the gases than the gases exert on it.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. In a rocket propulsion scenario where the rocket pushes gases left, both experience equal opposite forces: the gases accelerate left, and the rocket accelerates right; both change motion in opposite directions due to the interaction. Choice B is correct because it properly predicts both objects change motion based on both experiencing forces and accurately predicts direction of motion changes (opposite accelerations from opposite forces), with the rocket right and gases left. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate, claiming the rocket stays unchanged when actually the gases push it equally. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 7

Two ice skaters start at rest on smooth ice and push off each other.

Skater A has mass 50 kg. Skater B has mass 100 kg. During the push, they exert equal and opposite forces on each other for the same time.

Which prediction best compares their motion right after they push apart?

They move in the same direction because the forces are equal.
They both remain at rest because the forces are equal and cancel.
They move in opposite directions; the 50 kg skater has a larger speed because the same force causes a larger acceleration for the smaller mass ( $F=ma$ ). (correct answer)
They move in opposite directions; the 100 kg skater has a larger speed because heavier objects always move faster after a push.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart scenarios like two ice skaters pushing off from rest with unequal masses, both experience equal opposite forces (Newton's Third Law), so both accelerate away in opposite directions; the lighter 50 kg skater moves faster than the heavier 100 kg skater because F = ma gives larger acceleration for smaller mass (same F, smaller m → larger a), yet both are affected and both move. Choice C is correct because it correctly applies Newton's Third Law to conclude both objects affected and appropriately connects equal forces with different motion changes when masses differ, predicting opposite directions with the lighter having larger speed. Choice D is wrong because it bases prediction on mass only without considering forces, claiming heavier always moves faster, missing that forces are equal and both objects must respond but with accelerations inversely proportional to mass. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 8

A moving bowling ball rolls into a stationary bowling pin.

Before: ball moving forward; pin at rest. During: the ball pushes on the pin, and the pin pushes back on the ball with an equal and opposite force.

Which statement best explains why BOTH objects' motions change during the collision?

Only the pin changes motion because it is lighter; the ball feels no force from the pin.
Both change motion because each exerts a force on the other; the forces are equal and opposite (Newton's Third Law), so each can accelerate (Newton's Second Law). (correct answer)
The pin changes motion because the ball exerts a force, but the ball cannot change motion because it was already moving.
Both change motion because the ball's force is larger than the pin's force, so the pin moves more.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. When a heavy bowling ball hits a light stationary pin, both experience equal opposite forces (Newton's Third Law), causing both to accelerate (Newton's Second Law): the ball slows slightly, and the pin speeds up dramatically forward. Choice B is correct because it correctly applies Newton's Third Law to conclude both objects affected, explaining both change motion due to equal opposite forces leading to accelerations. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate, and claims the ball feels no force when actually the pin pushes back equally. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 9

Cart A (mass 4 kg) moves right at 2 m/s toward Cart B (mass 1 kg) that is at rest. They collide.

During the collision, the force on A from B and the force on B from A are equal in size and opposite in direction.

Which object has the greater acceleration (bigger change in motion per second) during the collision, and why?

Cart A, because the heavier object always has the greater acceleration in a collision.
Cart B, because the same force causes a larger acceleration for the smaller mass ( $a=F/m$ ), even though both forces are equal and opposite. (correct answer)
They have the same acceleration because the forces are equal, so $a$ must be equal too.
Neither cart accelerates because the forces are equal and cancel out between the carts.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For unequal masses where heavy Cart A (4 kg) hits light Cart B (1 kg), both experience equal forces, but the light Cart B undergoes larger acceleration (a = F/m, smaller m → larger a) and thus bigger motion change per second. Choice B is correct because it appropriately connects equal forces with different motion changes when masses differ, explaining the smaller mass has greater acceleration even though forces are equal and opposite. Choice C is wrong because it claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 10

Two carts on a low-friction track are connected by a compressed spring between them. They start at rest, then the spring is released and pushes them apart. Cart A has mass $1\,\text{kg}$ and Cart B has mass $4\,\text{kg}$ .

Which prediction is most accurate about their motions right after release?

Cart A and Cart B move in opposite directions; Cart A ends up with the larger speed because both experience equal and opposite forces but Cart A has the smaller mass ( $a=F/m$ ). (correct answer)
Both carts move in the same direction because the spring pushes them forward together.
Only Cart A moves because the spring is closer to Cart A, so Cart A gets all the force.
Cart B moves faster because the larger mass means the spring force on it is larger.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart: Two ice skaters push off each other from rest—both experience equal opposite forces (Newton's Third Law), so both accelerate away from each other in opposite directions. If they have equal masses, they move with equal speeds (one left, one right), but if one skater is heavier, the lighter skater moves faster and the heavier moves slower (F = ma: same F, smaller m gives larger a), yet both are affected and both move because both experienced forces. Choice A is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / accurately predicts direction of motion changes (opposite accelerations from opposite forces) / appropriately connects equal forces with different motion changes when masses differ. Choice B is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate / claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force / predicts motion changes in the same direction when the opposite forces should produce opposite accelerations / suggests the stationary or heavier object remains completely unaffected, when actually it experiences equal force and must accelerate (even if imperceptibly). Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 11

Two ice skaters start at rest on frictionless ice. Skater A has mass $50\,\text{kg}$ and Skater B has mass $100\,\text{kg}$ . They push off each other and separate.

Which prediction best describes what happens immediately after they push, and why?

Skater B moves faster because the heavier skater produces a larger force.
Skater A moves faster than Skater B; they push with equal and opposite forces, but the smaller mass has the larger acceleration ( $a=F/m$ ). (correct answer)
Only Skater A moves because Skater A is the one who decided to push first.
They both move away at the same speed because Newton's Third Law means they must have the same acceleration.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart: Two ice skaters push off each other from rest—both experience equal opposite forces (Newton's Third Law), so both accelerate away from each other in opposite directions. If they have equal masses, they move with equal speeds (one left, one right), but if one skater is heavier, the lighter skater moves faster and the heavier moves slower (F = ma: same F, smaller m gives larger a), yet both are affected and both move because both experienced forces. Choice B is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / accurately predicts direction of motion changes (opposite accelerations from opposite forces) / appropriately connects equal forces with different motion changes when masses differ. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate / claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force / predicts motion changes in the same direction when the opposite forces should produce opposite accelerations / suggests the stationary or heavier object remains completely unaffected, when actually it experiences equal force and must accelerate (even if imperceptibly). Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 12

A small rubber ball is thrown straight at a much more massive concrete wall.

Before: ball moves toward the wall; wall is at rest. During: ball and wall exert equal and opposite forces on each other.

Which prediction best describes the motion changes during the collision?

The wall exerts a force on the ball, but the ball does not exert any force on the wall.
Both experience equal and opposite forces, but the ball's motion changes much more (it may bounce back) because its mass is much smaller, so its acceleration is larger. (correct answer)
Both the ball and the wall bounce backward the same amount because the forces are equal.
The ball keeps moving forward through the wall because the wall is at rest and cannot push back.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For a light ball hitting a massive wall, both experience equal opposite forces (Newton's Third Law), but F = ma predicts different motion changes: the ball (small mass) undergoes large acceleration and bounces back, while the wall (huge mass) undergoes tiny acceleration and barely moves. Choice B is correct because it properly predicts both objects change motion based on both experiencing forces and appropriately connects equal forces with different motion changes when masses differ, with the ball changing much more due to larger acceleration. Choice A is wrong because it claims only one object exerts a force, violating Newton's Third Law which requires equal opposite forces on both, suggesting the ball feels force but wall does not when actually both do. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 13

A student stands on a skateboard (low friction) holding a heavy ball. The student throws the ball forward (to the right).

Before: student+skateboard and ball are at rest. During: the student pushes the ball right; the ball pushes the student left with an equal and opposite force.

Which statement best predicts what happens to BOTH the ball and the student right after the throw?

The ball moves right, and the student rolls left; both are affected because the forces during the throw are equal and opposite. (correct answer)
The ball moves right, but the student stays still because only the ball experiences a force.
The student rolls right with the ball because the student is the one doing the pushing.
Neither moves because the forces are equal and cancel out on each object.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. In a throw scenario like a student on a skateboard throwing a ball to the right, both experience equal opposite forces: the student pushes the ball right (causing it to move right), and the ball pushes the student left (causing the student to roll left); both motion states change due to the interaction. Choice A is correct because it properly predicts both objects change motion based on both experiencing forces and accurately predicts direction of motion changes (opposite accelerations from opposite forces), with the ball moving right and student left. Choice B is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate, suggesting the student stays still when actually the ball exerts an equal force back. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 14

A person stands on a skateboard at rest. The person throws a heavy backpack forward (to the right). Assume friction is very small.

What happens to the motion of both the backpack and the person+skateboard right after the throw, and why?

The backpack moves right and the person+skateboard moves left because they exert equal and opposite forces on each other during the throw. (correct answer)
The backpack moves right, but the person+skateboard stays at rest because only the backpack experiences a force.
Both the backpack and the person+skateboard move right because the person is pushing everything to the right.
Nothing moves because the forces are equal and cancel, so there is no motion change.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart: Two ice skaters push off each other from rest—both experience equal opposite forces (Newton's Third Law), so both accelerate away from each other in opposite directions. If they have equal masses, they move with equal speeds (one left, one right), but if one skater is heavier, the lighter skater moves faster and the heavier moves slower (F = ma: same F, smaller m gives larger a), yet both are affected and both move because both experienced forces. Choice A is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / accurately predicts direction of motion changes (opposite accelerations from opposite forces) / appropriately connects equal forces with different motion changes when masses differ. Choice B is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate / claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force / predicts motion changes in the same direction when the opposite forces should produce opposite accelerations / suggests the stationary or heavier object remains completely unaffected, when actually it experiences equal force and must accelerate (even if imperceptibly). Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.

Question 15

A bowling ball and a tennis ball roll toward each other on a smooth floor and collide head-on. The bowling ball has much greater mass than the tennis ball.

During the collision, which statement is correct about the forces and the motion changes?

The bowling ball exerts a larger force on the tennis ball, so the tennis ball changes motion more.
They exert equal and opposite forces on each other, but the tennis ball changes motion more because the same force causes a larger acceleration on the smaller mass. (correct answer)
The tennis ball exerts a force on the bowling ball, but the bowling ball exerts no force on the tennis ball because it is heavier.
Both objects must change their speeds by the same amount because the forces are equal.

Question 16

Two carts collide head-on on a low-friction track. Cart A (mass $3\,\text{kg}$ ) moves right at $2\,\text{m/s}$ . Cart B (mass $3\,\text{kg}$ ) moves left at $2\,\text{m/s}$ .

Right after they collide, which prediction best describes what happens to the motion of both carts?

Both carts keep their same speeds because the forces cancel out, so neither cart changes motion.
Only Cart A changes motion because it hits Cart B first.
Both carts experience equal and opposite forces, so both change motion; they slow down during the collision and may reverse direction depending on how the collision happens. (correct answer)
Both carts accelerate in the same direction because the collision force points the same way on both carts.

Question 17

An ice skater A (mass $50\,\text{kg}$ ) and an ice skater B (mass $100\,\text{kg}$ ) start at rest on smooth ice. They push off each other with their hands and then glide apart.

Which statement best predicts their motion right after the push?

Skater A and Skater B move in opposite directions; Skater A moves faster because both feel equal forces but A has smaller mass so larger acceleration. (correct answer)
Skater B moves faster because the heavier skater creates a bigger force on the lighter skater.
Only Skater A moves because Skater A is lighter and is easier to move.
Both skaters move in the same direction because the forces during the push are in the same direction on both skaters.

Question 18

A rocket in space fires its engine. Hot gases are pushed out the back of the rocket (to the left), and the rocket speeds up to the right.

Which statement best explains why both the rocket and the gases change motion?

Only the gases experience a force because they are the part that is moving.
The rocket pushes the gases left, and the gases push the rocket right with an equal and opposite force; both accelerate in opposite directions. (correct answer)
The gases push harder on the rocket than the rocket pushes on the gases, which is why the rocket moves forward.
No forces act because the rocket is in space and there is nothing to push against.

Question 19

A heavy cart A (mass $6\,\text{kg}$ ) moves right at $3\,\text{m/s}$ and hits a lighter cart B (mass $2\,\text{kg}$ ) that is at rest on a low-friction track.

Which statement best compares the motion changes of the two carts during the collision?

Cart B will have a larger change in motion than Cart A because both feel equal forces, but Cart B has smaller mass so it accelerates more ( $F=ma$ ). (correct answer)
Cart A will have a larger change in motion because heavier objects always change speed more in collisions.
Only Cart B changes motion because Cart A is moving and Cart B is not.
Cart B changes more because Cart A exerts a bigger force on B than B exerts on A.

Question 20

A small rubber ball is thrown straight at a heavy concrete wall. The ball hits the wall and bounces back.

Which statement best explains why both the ball and the wall experience forces during the collision, even though the wall's motion doesn't noticeably change?

Before: ball →, wall at rest During: contact forces After: ball ←, wall ~unchanged

The wall exerts a force on the ball, but the ball does not exert any force on the wall because the wall is not moving.
The ball exerts a force on the wall and the wall exerts an equal and opposite force on the ball (Newton's Third Law); the wall's acceleration is tiny because its mass is very large ( $a=F/m$ ). (correct answer)
The ball bounces back because only the ball has a force on it; the wall has no force because it is attached to the ground.
The wall exerts a bigger force than the ball, which is why the ball reverses direction while the wall does not.

Explanation: This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For unequal masses: If a light ball collides with a heavy wall, both experience equal forces during collision (Newton's Third Law), but F = ma predicts different motion changes: the ball (small mass) undergoes large acceleration and bounces back dramatically with high speed, while the wall (large mass) undergoes small acceleration and barely moves. Both motion states change—the ball reverses direction (large change), the wall moves slightly (small change)—but the forces were equal; the mass difference accounts for the different motion changes (same F, different m → different a). Choice B is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / appropriately connects equal forces with different motion changes when masses differ. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.