Practice Test 7 - 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 solid cylinder and a hoop (same mass and radius) each experience the same net counterclockwise torque and accelerate counterclockwise. Which has the greater angular acceleration?
2. A block slides up a rough incline after being launched upward, slowing as it moves. The friction is kinetic; other forces are weight and the normal force. What is the direction of the kinetic friction force on the block?
3. A mass on a vertical spring is displaced downward by $y$ from equilibrium. Experiments show the net force relative to equilibrium is $F=-ky$ (gravity and spring stretch at equilibrium already balance). Neglecting air resistance, is the motion simple harmonic?
4. A constant horizontal force $F$ moves an object at constant speed $v$ for time $t$. In a second trial, the force is $2F$ and the speed is $v/2$ for the same time $t$. Compare average powers.
5. A rigid arm pivots at point $P$. A force $F$ is applied at a point a distance $r$ from $P$. The force's line of action is perpendicular to the arm, so the lever arm equals $r$. If the application point is moved to $2r$ while keeping $F$ perpendicular and unchanged, the torque magnitude about $P$ becomes
6. A wrench pivots about the center of a bolt. A force is applied at the end of the handle. The line of action is perpendicular to the handle, and the lever arm is $0.20\,\text{m}$. If the same force is applied at a point closer to the bolt so the lever arm is $0.10\,\text{m}$, how does the torque magnitude change?
7. A moving cart collides with a stationary cart on a nearly frictionless track. After the collision, the carts move together as a single unit. What can be concluded about kinetic energy in the collision?
8. A ball rolls off a $1.2\,\text{m}$-high table with a horizontal velocity. Neglect air resistance. As it falls, the vertical component of velocity increases downward due to gravity while the horizontal component has no acceleration. Which statement about the ball's horizontal velocity is correct just before it hits the floor?
9. Water flows steadily through a horizontal pipe and is incompressible. At section 1 the cross-sectional area is $2A$ and the speed is $v$. At section 2 the area is $A$. For this steady, incompressible flow, what is the speed at section 2?
10. A spring ($k$) launches a block ($m$) on a frictionless horizontal surface from compression $x$. What is the block's speed when the spring reaches equilibrium?
11. A block slides down a rough incline at constant speed. The friction is kinetic; other forces are weight and the incline's normal force. Which statement about the kinetic friction magnitude is correct?
12. A block on a track is pulled toward equilibrium by a force that always has magnitude $F_0$ and direction opposite the displacement $x$ (so $F=-F_0\,\text{sgn}(x)$). The block oscillates back and forth. Is the motion simple harmonic?
13. Two same-volume containers are sealed. Container $X$ has smaller mass than container $Y$. Which inference about average density is supported?
14. A wheel rolls without slipping with center-of-mass speed $v$. What is the magnitude of the velocity of the point at the wheel's center?
15. A disk rotates about a fixed central pivot. A student applies a constant tangential force at the rim that produces a counterclockwise torque, but the disk remains at rest with no angular displacement. Which statement about the work done by the torque from the force is correct?
16. A student claims that as a projectile rises, its horizontal speed decreases because its vertical speed decreases. In ideal projectile motion, the horizontal and vertical components evolve independently. Which statement best refutes the claim?
17. A cyclist moves along a straight road; positive is east. A velocity–time graph is a straight line decreasing from $v=+6\,\text{m/s}$ at $t=0\,\text{s}$ to $v=0\,\text{m/s}$ at $t=3\,\text{s}$. What is the cyclist's displacement from $t=0$ to $t=3\,\text{s}$?
18. A skydiver has reached terminal velocity and continues falling straight down at constant speed. The forces on the skydiver are gravity downward and air resistance upward. The speed remains constant. Which statement about these forces is correct?​
19. A wheel rotates freely with angular speed $_0$ and negligible external torque. A second identical wheel, initially not rotating, is dropped coaxially onto it; they stick together. What is the final angular speed?
20. Two identical balls leave a ledge simultaneously: one is dropped, one is launched horizontally. Ignoring air resistance, which hits the ground first?

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