Practice Test 3 - 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 mass–spring oscillator moves in SHM with no friction. At maximum displacement from equilibrium, the mass is momentarily at rest, so kinetic energy is zero and spring potential energy is maximum. At equilibrium, kinetic energy is maximum and potential energy is minimum, with total mechanical energy constant. At maximum displacement, which statement is correct?
2. A cylinder rolls without slipping at speed $v$. What is the instantaneous speed of the point in contact with the ground?
3. A cylinder rolls without slipping at speed $v$. What is the speed of the leftmost point on the rim relative to the ground?
4. A student pushes a cart with constant horizontal force $F$ at constant speed $v$ for distance $d$. Which change increases average power?
5. A block attached to a spring oscillates in SHM on a frictionless surface. At equilibrium, the block's kinetic energy is $K_0=3\,\text{J}$ and its spring potential energy is $0\,\text{J}$. At maximum displacement it is momentarily at rest. What is the spring potential energy at equilibrium?
6. A student pushes a box across a floor, then stops pushing. Immediately after the push ends, the box continues moving but slows down. During this slowing interval, the box interacts with Earth (gravity), the floor (normal and kinetic friction), and air (drag). Which statement about the net force is correct during the slowing interval?
7. A fan has constant angular acceleration $\alpha=3\ \text{rad/s}^2$ and starts from rest. After $4\ \text{s}$, what is $\omega$?
8. A box on a rough floor is pulled to the right with a $10\,\text{N}$ force but remains at rest. The friction is static; other forces are weight and normal force. If the pull is reduced to $7\,\text{N}$ and the box still does not move, what happens to the static friction magnitude?
9. A projectile is launched and later passes through two points at the same height on its way up and down. Neglect air resistance: the horizontal component of velocity is constant, while the vertical component changes sign. At those two points, which statement is correct?
10. A turntable rotates at constant $\omega=5\ \text{rad/s}$ for $4\ \text{s}$. What is the angular displacement $\Delta\theta$?
11. On a straight track, cart $A$ has mass $m$ and moves east at speed $3v$. Cart $B$ has mass $2m$ and moves west at speed $v$. Taking east as positive, which cart has the greater momentum magnitude?
12. A magnet is held near a steel paper clip, and the paper clip is attracted toward the magnet. Consider the interaction between the magnet and the paper clip. Which statement correctly compares the forces they exert on each other?
13. A student tosses a ball so its path is a parabola. At some instant, the ball has a rightward horizontal velocity component and an upward vertical component. Neglect air resistance. Which best explains why the path curves downward?
14. Two mass–spring oscillators have the same mass $m$, but spring constants $k$ and $4k$. Which has the greater frequency?
15. A moon moves in a circular orbit around a planet. At point Z, its velocity is tangent east. Which statement about the moon's instantaneous acceleration vector is correct?
16. A uniform door rotates about a vertical hinge at its left edge (pivot). A student pushes on the door at the handle, $0.80\,\text{m}$ from the hinge. The push is horizontal and its line of action makes an oblique angle (neither parallel nor perpendicular) with the door, so the lever arm is less than $0.80\,\text{m}$. If the student instead pushes with the same force perpendicular to the door at the same point, how does the torque about the hinge change?
17. A block is suspended in water by a string from above and is at rest. Forces are buoyant force upward, tension upward, and weight $mg$ downward. Which must be true?
18. A mass on a spring is displaced. The restoring force is measured as $F=-2kx$ when stretched but $F=-kx$ when compressed. Is the motion SHM?
19. A book on a rough table is pulled horizontally with a force that gradually increases. Just before the book begins to move, the friction is static; other forces are weight and normal force. At that instant, the static friction magnitude is best described as
20. A mass hangs from a vertical spring. At $x=0$ (unstretched), define $U_s=0$. At $x=0.30\,\text{m}$ stretch, what is true?

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