Practice quiz · by a Quizcard user

AP Physics 1: Energy, Momentum and Rotation — quiz

15 multiple-choice questions covering Work, Work-Energy Theorem, Gravitational Potential Energy, Conservation of Energy, Power. One answer each; you get a score at the end and the explanation for every question. No account needed.

Updated 2026-11-03. Keys 1–4 pick an answer, Enter moves on. Redo it any time, in order or shuffled.

The questions

Answers and explanations are shown after you finish.

1. Work

   A crate is dragged across a floor by a rope angled 30° above horizontal while the crate also experiences a normal force from the floor. Which force necessarily does zero work on the crate as it slides?

   • Friction force
   • Applied force at the angle
   • Normal force from the floor
   • Tension in the rope
2. Work-Energy Theorem

   A box slides across a table under an applied force, friction, gravity, and a normal force. To correctly find the box's final kinetic energy using the work-energy theorem, which work value should be used?

   • Work done only by the applied force
   • Net work done by all forces acting on the box
   • Work done by friction alone
   • Work done by gravity alone
3. Gravitational Potential Energy

   One student calculates a ball's gravitational PE using the floor as the zero reference and gets 50 J at tabletop height. A second student uses the tabletop itself as the zero reference. Which statement correctly describes the relationship between their results?

   • Both students must obtain the identical PE value at the tabletop
   • The two students will get different absolute PE values, but identical changes in PE between any two heights
   • The second student's calculation is invalid since PE must always be positive
   • PE cannot be calculated unless the floor is used as the reference
4. Conservation of Energy

   A block slides down a ramp with friction present between the block and the surface. Which equation correctly relates its energy at the top and bottom of the ramp?

   • KE_i+U_i+W_nc=KE_f+U_f, accounting for friction's work
   • Change in KE always equals initial PE, regardless of friction
   • Final KE equals initial PE exactly
   • KE_i+U_i=KE_f+U_f, assuming no energy is lost
5. Power

   A car's engine exerts a 500 N force in the direction of motion at the instant the car's speed is 20 m/s. What is the instantaneous power output at that moment?

   • Cannot be determined without knowing the average velocity over the entire trip
   • 20 W
   • 10,000 W
   • 500 W
6. Impulse-Momentum Theorem

   During a car crash, an airbag increases the time over which a passenger's momentum changes to zero. According to the impulse-momentum theorem, what effect does this have?

   • It increases the passenger's change in momentum
   • It has no effect, because impulse depends only on force, not time
   • It decreases the total impulse delivered to the passenger
   • It decreases the average force experienced by the passenger
7. Impulse from F–t Graph

   A force-time graph shows a positive force from t=0 to 2s and a negative force from t=2s to 4s. How should total impulse be found from this graph?

   • Ignore the negative-force region entirely
   • Add the magnitudes of both areas together
   • Subtract the negative-force region's area from the positive-force region's area
   • Average the two areas to get total impulse
8. Conservation of Momentum

   Two carts collide on a frictionless track. After the collision, total kinetic energy is lower than before, but students still measure the same total momentum as before. Which statement correctly explains this result?

   • The students must have made an error, since lost KE implies lost momentum too
   • This is impossible; momentum must decrease whenever KE decreases
   • Momentum conservation requires only that net external force be zero, regardless of whether KE is conserved
   • Momentum is only conserved in perfectly elastic collisions
9. Perfectly Inelastic Collisions

   A 2 kg cart moving at 4 m/s collides with an identical stationary 2 kg cart, and they stick together after impact. What is their common final velocity?

   • 4 m/s
   • 8 m/s
   • 2 m/s
   • 1 m/s
10. Center of Mass

    A firework shell explodes in midair into several fragments that scatter in different directions under gravity's influence alone. What happens to the center of mass of the fragments immediately after the explosion?

    • The center of mass immediately stops moving
    • The center of mass follows an unpredictable new path
    • The center of mass moves only toward the heaviest fragment
    • The center of mass continues along the same projectile trajectory as before the explosion
11. Torque and Equilibrium

    A uniform beam is held in static equilibrium by two supports, one of which exerts an unknown force. To solve for the unknown force most efficiently using the torque equation, where should the pivot be placed?

    • At the beam's center of mass
    • Pivot location doesn't matter since torque is undefined except about the center of mass
    • At the point where the unknown force acts, so its torque term drops out
    • At the location of a known applied force
12. Rotational Kinematics

    A student uses ω=ω₀+αt with angular position and velocity measured in degrees instead of radians to predict a wheel's motion. What is the issue with this approach?

    • Nothing is wrong; the equations work with any angular unit
    • This issue only affects angular acceleration calculations, not angular velocity
    • The equations and relations like v=rω require angles in radians for the units to be consistent
    • Degrees simply give answers that are too large in magnitude
13. Moment of Inertia

    A rod of mass M and length L can be rotated either about its center or about one end. Which statement correctly compares the two moments of inertia?

    • The moment of inertia about the end is four times that about the center, since mass is farther from the axis
    • Moment of inertia does not depend on the axis of rotation
    • The moment of inertia about the center is larger since it passes through more mass
    • The moment of inertia is the same about either axis
14. Rotational Kinetic Energy

    A solid ball rolls without slipping down a hill, gaining both linear and rotational speed. Which expression correctly gives the ball's total kinetic energy at the bottom?

    • The total KE is the product of ½mv² and ½Iω²
    • ½mv² alone accounts for all the kinetic energy
    • ½Iω² alone accounts for all the kinetic energy
    • The ball's total KE is the sum of ½mv² (translational) and ½Iω² (rotational)
15. Conservation of Angular Momentum

    A diver in midair pulls her body into a tuck position, decreasing her moment of inertia, with no external torque acting during the dive. What happens to her angular momentum and rotational kinetic energy during the tuck?

    • Both angular momentum and rotational KE stay constant
    • Both angular momentum and rotational KE decrease
    • Angular momentum increases while rotational KE stays constant
    • Angular momentum stays constant while rotational KE increases