# Angular acceleration of a skater

1. Nov 2, 2005

Hi,
I need help with the following problem.

A skater does a pirouette at the rate of 2.0 rev / second and then stop within 3/4 rev. Assume that the angular decceleration is constant and calculate its magnitude.

I tried to compute it but I found -18 rad/s2.
BUt the textbook gives -17 rad/s2.
Please can someone help me with this problem?

Thank you
B

2. Nov 2, 2005

### andrevdh

use
$$\omega^2 \ = \ {\omega^2}_o \ + \ 2\alpha \ \Delta\theta$$
The rotational equivalent of
$$v^2 \ = \ {v^2}_o \ + \ 2as$$

Last edited: Nov 2, 2005
3. Nov 2, 2005

### Staff: Mentor

What formula did you use to compute 18 rad/s2?

What is the angular analogy to v2 = vo2 + 2ax?

The 17 rad/s would be rounded.

4. Nov 2, 2005