Answer to Question #276912 in Mechanics | Relativity for Nika Galanida

Question

A figure skater is spinning at an angular velocity of 8.0 rad/s. Assume that her moment of inertia is 80 kg/m2.

a. What is the angular momentum of the figure skater?

b. How much torque is required to slow her down to a stop in 5.0 seconds?

Answer 1

(a) We can find the angular momentum as follows:

$$L=I\omega=80\ kg\times m^2\times8.0\ \dfrac{rad}{s}=640\ \dfrac{kg\times m^2}{s}.$$

(b) We can find the amount of torque as follows:

$$\tau=\dfrac{\Delta L}{\Delta t}=\dfrac{0-640\ \dfrac{kg\times m^2}{s}}{5\ s}=-128\ N\times m.$$