Answer:
<em>a) 2.63 : 1</em>
<em>b) 143.13 rpm</em>
Explanation:
initial angular velocity ω' = 130 rpm
final angular velocity ω = 342 rpm
recall that angular momentum = ωI
where I is the moment of inertia.
for the initial spinning condition, we take moment of inertial = I'
for final spinning condition, we take moment of inertia = I
initial angular momentum = ω'I' = 130 I'
final angular momentum = ωI = 342 I
according to conservation of angular momentum, initial angular momentum must be equal to the final angular momentum, therefore
342 I = 130 I'
ratio of initial moment of inertia to final moment of inertia = I'/I
==> I'/I = 342/130 ≅ <em>2.63 : 1</em>
b) to achieve a final angular velocity of of 375 rpm, her initial velocity will have to be
2.63 = 375/ω'
ω' = 375/2.63 = <em>143.13 rpm</em>
