Practice Test 6 - AP Physics 1

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

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1. A swimmer pushes backward on the pool wall during a turn. The wall pushes forward on the swimmer during the same contact. While the swimmer's feet are in contact with the wall, how do the magnitudes of these two forces compare?
2. Two ice skaters initially at rest on frictionless ice pull on a rope between them. The system boundary includes both skaters and the rope; the rope tension forces are internal, and external horizontal forces are negligible. As they move toward each other, what happens to the system's center of mass?
3. A rigid bar rotates about a vertical axle through its center. Keeping $\omega$ the same, two equal masses are slid outward along the bar, farther from the axis. What happens to rotational kinetic energy?
4. A 5.0 kg crate is pulled across a rough floor by a person using a horizontal rope. Consider the interaction forces between the rope and the crate at the attachment point. How does the force exerted by the rope on the crate compare to the force exerted by the crate on the rope?
5. A person stands on a bathroom scale in an elevator. The person's feet push down on the scale, and the scale pushes up on the person. At a given instant (regardless of whether the elevator is speeding up or slowing down), how do these two forces compare in magnitude?​
6. A hoop rolls without slipping so that $\omega$ increases. What must happen to the center-of-mass speed $v$ (radius $R$ constant)?
7. A velocity–time graph for SHM shows $v$ crossing zero at $t=0$ with a positive slope. Equilibrium is at $x=0$. At $t=0$, where is the mass relative to equilibrium?
8. Car A and car B each experience the same driving force $F$ on level ground. Car A moves at speed $v$ and car B at $2v$. Compare power.
9. A block on a rough horizontal surface is pushed to the right with $4\,\text{N}$ and remains at rest. The friction is static; other forces are weight and normal force. Which statement about the friction magnitude is necessarily true?
10. A wheel of radius $R$ rolls without slipping with center-of-mass speed $v$. What is its angular speed $\omega$?
11. A disk rotates freely with angular speed $\omega_0$ about its center. External torque is negligible. Clay is dropped onto the disk and sticks, increasing the total rotational inertia to $1.25I_0$. What is the disk's new angular speed?​
12. Take positive $x$ to the right. A toy car moves with constant speed $2\,\text{m/s}$ for $5\,\text{s}$, then reverses direction at the same speed for $5\,\text{s}$. Which is correct?
13. A pendulum swings with large amplitude, and its tangential acceleration follows $a_t=-g\sin\theta$. Is the motion simple harmonic?
14. A cart moves off a ramp and becomes a projectile. While in the air, a student claims the cart's decreasing vertical speed causes its horizontal speed to decrease too. Which statement best evaluates this claim?
15. Two circular objects of equal mass $M$ rotate about the same axis through the center, perpendicular to the plane. Object 1 is a thin ring of radius $R$. Object 2 is a thin ring of radius $2R$. Which object has the greater rotational inertia about the axis?
16. Two satellites of masses $m$ and $2m$ move in the same circular orbit of radius $r$ around a planet. At point P, both velocities are tangent east. Which satellite has the greater centripetal acceleration?
17. A 2.0 kg book rests on a table. The book and table exert contact forces on each other at the surface. How does the force exerted by the table on the book compare to the force exerted by the book on the table?
18. Two students pull on opposite ends of a rope tied to a 4.0 kg box on a frictionless floor. Student 1 pulls right with 12 N; Student 2 pulls left with 5.0 N. The box accelerates right. Which forces act on the box? Stem: Which set of forces correctly represents the free-body diagram of the box?
19. A constant net force of magnitude $8\,\text{N}$ acts on an object for $0.75\,\text{s}$, in the direction of motion. What is the magnitude of $\Delta \vec p$?
20. A crate is pulled across a rough horizontal floor by a rope. After a brief start-up, it moves to the right at constant speed. During this constant-speed interval, the crate interacts with Earth (gravity), the floor (normal and kinetic friction), and the rope (tension). Which statement about horizontal forces is correct?

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