Conservation of Angular Momentum — Practice Quiz

Question 1

An ice skater with arms out (I = 5 kg·m², ω = 2 rad/s) pulls them in (I = 2 kg·m²). New ω:

Accepted Answer

5 rad/s

Answer

0.8 rad/s

Answer

10 rad/s

Answer

4 rad/s

Question 2

KE of the skater after pulling arms in changes by factor:

Accepted Answer

I₁/I₂ = 2.5

Answer

Same

Answer

I₂/I₁ = 0.4

Answer

Doubles

Question 3

Earth's day length is slowly INCREASING because:

Accepted Answer

Tidal friction transfers L from Earth's rotation to the Moon's orbit

Answer

Earth is heating

Answer

Earth is growing

Answer

Magnetic effect

Question 4

Conservation of L requires:

Accepted Answer

No external torque

Answer

No external force

Answer

Constant velocity

Answer

Symmetric body

Question 5

A pulsar (collapsed star) has ω ~ 600 rad/s. The original star had ω ~ 10⁻⁶ rad/s. Ratio of R_old to R_new (assuming uniform sphere):

Accepted Answer

~10⁴ (I scaled as R², ω inversely as R²)

Answer

~10⁻³

Answer

~10⁻⁹

Answer

Cannot determine