AP Physics 1 — Unit 6: Energy and Momentum of Rotating Systems
Practice questions, answers, and key terms for Unit 6, aligned to the College Board CED.
AP Physics 1 Unit 6 practice questions
A fidget spinner whirls in place without going anywhere. It still has energy of motion. How do you calculate it?
KE_rot = ½Iω², with I the rotational inertia. It mirrors ½mv² with I for m and ω for v.
Two wheels have the same mass and spin at the same ω, but one has its mass packed near the rim. Which stores more rotational KE?
The rim-loaded wheel — its mass sits farther out, raising I. KE_rot = ½Iω² scales with I.
A bowling ball rolls across the floor. A friend says its KE is just ½mv². What are they leaving out?
The rotational part. A rolling object's total KE = ½mv_cm² + ½Iω², so they're ignoring the spin energy.
Angular velocity and angular momentum point along an axis, but a friend insists rotational KE must point that way too. Why are they wrong?
Rotational KE is a scalar with no direction. It has magnitude only, unlike ω or L.
You push a merry-go-round at the edge versus right next to the center pole, with the same force. Why does the edge spin it up faster?
Torque τ = rF sinθ, which is larger at the edge. A bigger r there means more torque for the same force.
You pull on a wrench but the bolt won't budge. The force points straight along the wrench handle, toward the bolt. Why is there zero torque?
Torque = rF sinθ, and θ = 0° here, so sinθ = 0 and τ = 0. Force along the lever arm twists nothing.
A motor spins a wheel through an angle while applying constant torque. How much work did the torque do?
W = τΔθ, the rotational analog of linear W = Fd. Δθ is the angle turned in radians.
A spinning ice skater has 'rotational momentum.' What's the actual formula for the angular momentum of a rotating rigid body?
L = Iω, rotational inertia times ω. It mirrors linear momentum p = mv.
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Key terms in Unit 6
These 12 terms show up in the Unit 6 cards. Each one links to its definition in the AP Physics 1 key-term reference.
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