Practice Test 4 - Middle School Physical Science

20 questions. Answer them in any order, then submit to see your score and every explanation.

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1. A sound wave is shown on a pressure vs. time graph. The equilibrium (rest) pressure is atmospheric pressure, and the graph's center line is labeled $101{,}325\text{ Pa}$. The maximum compression reaches $101{,}335\text{ Pa}$ and the minimum rarefaction reaches $101{,}315\text{ Pa}$. What is the amplitude of the pressure wave?
2. A student maps a magnetic field by placing a compass at points on a grid around a bar magnet and drawing an arrow at each point showing the direction the compass needle points. The arrows form a smooth, curved pattern that changes direction from place to place. What does the pattern of arrows best represent?
3. A student drops a ball from shoulder height. While the ball is falling, it is not touching the ground yet, but it speeds up downward toward Earth. This is evidence that which force can act without direct contact?
4. A remote control sends commands to a TV using infrared light (a type of electromagnetic wave). The remote flashes the infrared light in a specific pattern, and a sensor on the TV reads it. What is the BEST explanation of how the command is encoded?
5. A student says, "When a truck hits a small car, the truck exerts a bigger force on the car than the car exerts on the truck." Which response best uses Newton's Third Law to evaluate this claim?
6. Electric and magnetic forces can either attract or repel. Why is gravity different from these forces in everyday situations?
7. A student makes a KE vs speed graph for a constant-mass object. When speed increases from 1 m/s to 2 m/s, KE increases from 1 J to 4 J. When speed increases from 3 m/s to 4 m/s, KE increases from 9 J to 16 J. What does this show about the graph's steepness as speed increases?​
8. Sunlight shines on a dark sidewalk at noon. The sidewalk gets noticeably warmer even though space between the Sun and Earth is mostly a vacuum. How does energy transfer from the Sun to the sidewalk?
9. A student pushes a heavy crate across the floor at a constant speed. The push is forward, and friction is backward. The crate's speed does not change. Which statement best connects work and kinetic energy in this situation?​
10. A model shows a water molecule (H₂O) and a carbon dioxide molecule (CO₂). Which statement is true about what they have in common?
11. A student investigates: How does the mass of a cart affect how fast it rolls down a ramp? The student adds different numbers of washers to the same cart, releases it from the same starting line, and measures the cart's speed at the bottom. Which variable is the independent variable in this investigation? Independent: [what you change] Dependent: [what you measure] Controlled: [what you keep the same]
12. A student breaks a crystal of table salt into two smaller pieces. Which statement best describes what happens at the particle level?
13. Two students discuss why a 1 kg object weighs 25 N on Jupiter but only 3.7 N on Mars. Which explanation is best?
14. A window in winter loses heat from a warm room to the cold outdoors by conduction through glass, convection from air leaks and air movement near the glass, and radiation from warm surfaces to colder ones. Which window upgrade best reduces heat loss by addressing all three methods?
15. A soccer ball is kicked forward and follows a curved path that eventually brings it back to the ground. If gravity suddenly disappeared right after the kick (and you ignore air resistance), what would the ball most likely do?
16. A student leaves an iron nail outside for several weeks. Before: - Nail is shiny gray metal - Surface is smooth After: - Nail has a reddish-brown coating - The coating is rough and flaky - The nail looks dull and does not return to shiny gray when wiped with a dry cloth Which statement best describes what happened?
17. A constant net force is applied to an object, and its mass is doubled while the force stays the same. According to $a=F/m$, what happens to the object's acceleration?
18. Cart A (2 kg) rolls to the right and collides with stationary Cart B (2 kg). During the collision, force sensors on each cart record: $F_{B\text{-on-}A}=10\,\text{N}$ to the left and $F_{A\text{-on-}B}=10\,\text{N}$ to the right. What do these measurements tell you about the forces during the collision?
19. A student uses the equation $Q = mc\Delta T$ to describe heating. Two beakers of water are heated by the same burner for the same amount of time, so they receive the same heat energy $Q$. Beaker 1 has 100 g of water; Beaker 2 has 200 g of water. Which statement is correct about their temperature changes?​
20. Design challenge (insulated lunch container): You are deciding how to test whether your insulated lunch container minimizes thermal energy transfer. Which test plan best matches the criterion "maintain food temperature for at least 4 hours" using simple classroom tools?

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