Torque required to slow down an object

1. Nov 21, 2011

Smartguy94

1. The problem statement, all variables and given/known data
What is the angular momentum of a figure skater spinning (with arms in close to her body) at 3.32 revolutions per second, assuming her to be a uniform cylinder with a height of 1.41 m, a radius of 13.4 cm, and a mass of 50.4 kg.

How much torque is required to slow her to a stop in 4.57 s, assuming she does not move her arms?

2. Relevant equations

I= (M x R^2) /2

3. The attempt at a solution

I got the first one, the angular momentum

since I= (M x R^2) /2
and w = 3.32*2∏

L = Iw
9.4 kg*m^2/s

ang acc is total change in ang vel divided by total time for uniform angular acceleration

α= w/4.57
torque = Iα
torque = 2.065N*m

but its wrong

anyone can help pls? thanks

Last edited: Nov 21, 2011