Question

An ice skater spins at 2.5 rev/s when his arms are extended.He draws his arms in and spins at 6.0 rev/s. By what factor doeshis moment of inertia change in the process?
A) 2.4
B) 1.0
C) 0.42
D) 0.12
E) 0.10

Answer 1

To solve this problem we will apply the concept related to Angular momentum. Said conservation momentum says that its initial state must be equal to that of the final state, that is,

$L_f = L_i$

$\omega_f I_f = \omega_i I_i$

Here,

I = Moment of Inertia

$\omega =$ Angular velocity

Rearranging to find the ratio between the moment of inertia we have,

$\frac{I_f}{I_i} =\frac{\omega_i}{\omega_f}$

Replacing,

$\frac{I_f}{I_i}= \frac{2.5}{6.0}$

$\frac{I_f}{I_i} = 0.42$

Therefore the correct option is C.