AP Physics 1 · Unit 6 · Rotating Systems

Conservation of Angular Momentum Practice Problems

Track the same total angular momentum through changing inertia and internal interactions.

12 questions6 conceptual · 6 calculation

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Simulation scene from the Conservation of Angular Momentum lesson. — A scene from the related lesson. Open the practice to work through the questions.

What you’ll practice

Use conservation with a clear system and axis

Identify the conservation condition

Choose the complete system and fixed axis, then check the net external angular impulse. Distinguish a force through the axis from a torque about that axis.

Add every angular-momentum contribution

Combine rotating disks, an incoming point mass, or opposite wheel and student contributions using one sign convention. Include the inertia of objects added during a sticking collision.

Compare energy and motion

Predict how angular speed responds to changing inertia. Calculate orbital endpoint speeds and the work needed to start a walker and turntable from rest.

A question from this set

Start with the system and axis

Two disks exchange frictional torques on a common frictionless axle. Which condition allows the total angular momentum of both disks to remain constant about that axle?

Zero net external angular impulse about the axle.
No forces may act anywhere on either disk.
The total kinetic energy must remain constant.

Try it in the practice set

Choose both disks as the system and compare internal friction with an external bearing torque.

Key ideas

Angular momentum can stay fixed while energy changes

Internal torque transfers angular momentum

Friction between disks and foot contact on a turntable redistribute angular momentum inside the selected system. Individual components can change while the total remains constant.

Changing inertia changes angular speed

A contracting cloud or inward-moving masses can rotate faster without an external torque. Internal work or gravitational energy can increase kinetic energy even as Iω remains constant.

See the physics

Watch angular momentum transfer between components

After an attempt, run the native models and compare component angular momenta with their sum. Track energy lost during synchronization or capture, energy gained during inward redistribution, and near and far orbit measurements. The wheel model displays vertical-component transfer with separately drawn axial degrees of freedom.

Use a hint for a starting point or open a worked solution to follow the reasoning. Your progress saves in this browser, so you can return to unfinished questions.

Ready for conservation of angular momentum?

Begin with a conceptual question, then work through the calculations.

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