Angular Momentum & Conservation – AP Physics C | ShowMeClass

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Angular Momentum & Conservation

AP Physics C · Unit 5: Rotation

Learning Objectives

Define angular momentum: L = Iω

Apply conservation: L₁ = L₂ when τ_net = 0

Relate τ = dL/dt (rotational Newton's 2nd law)

Explore ice-skater effect: I↓ → ω↑

Key Equations

Ice-Skater Effect

When a skater pulls arms in:
I decreases → ω increases
L = Iω stays constant

Use the Arm Radius slider to simulate pulling arms in/out.

Graph Colors

L — Angular momentum

ω — Angular velocity

I — Moment of inertia

KE_rot — Rotational KE

Angular MomentumConservationTorqueAP Physics C

L =—

ω =—

I =—

KE =—

L, ω, I vs ARM RADIUS

Scenario

Body Mass (kg) 50

Arm Radius (m) 0.8

Arm Mass (kg) 5

Initial ω₀ (rad/s) 3

Disk Radius (m) 0.5

Point Mass (kg) 2

Point at r (m) 0.3

Display

Angular Momentum Analysis

📝 Quick Quiz▼

1. When an ice skater pulls arms in (no external torque), angular momentum:

Increases Decreases Stays the same Becomes zero

2. τ = dL/dt is the rotational analog of:

W = Fd F = ma = dp/dt KE = ½mv² p = mv

3. If I is halved and L is conserved, ω:

Halves Doubles Quadruples Stays the same