# Angular momentum help

1. Jun 16, 2009

### jmb07

A turntable has mass 4.96 kg and a radius of 0.092 m and is spinning with a frequency of 0.53 rev/s. What is the angular momentum??

As simple as this problem seems, I just cannot seem to get the correct answer...here is what i have so far:

I (for a disc) = (1/2)(mr^2)
L = I(omega)
I also know that angular momentum = frequency x I

So,
0.53rev/s(.5 x 4.96kg x 0.092^2) = 0.011 (kgm^2)/s
However the correct answer is 0.0699....what am i doing wrong???

2. Jun 16, 2009

### Staff: Mentor

L = Iω, where ω is in radians/sec.

Convert to proper units.

3. Jun 16, 2009

### diazona

The frequency is in revolutions per second; you need to convert it into radians per second. The conversion factor is $2\pi\ \text{radians} = 1\ \text{revolution}$.

4. Jun 16, 2009

thanks!