What is the angular momentum of the record?

[ryty]

Homework Statement

A .019 kg record with a 15 cm radius rotates with an angular speed of 33 1/3 rpm. What is the angular momentum?

Homework Equations

L=Iw I=mr^2 w=(33.33/60)*2pi=3.17 rad/s

The Attempt at a Solution

L=(.019*.15^2)(3.17)
L=.0004275*3.17
L=.00136
but that's wrong, and i don't know why

 

[hage567]

Homework Statement

A .019 kg record with a 15 cm radius rotates with an angular speed of 33 1/3 rpm. What is the angular momentum?

Homework Equations

L=Iw I=mr^2 w=(33.33/60)*2pi=3.17 rad/s

The Attempt at a Solution

L=(.019*.15^2)(3.17)
L=.0004275*3.17
L=.00136
but that's wrong, and i don't know why

Check your calculation of your conversion to rad/s, I get a different number. Also, check that you are using the appropriate formula for the moment of inertia. Are you assuming the record is a solid disk? If so, your formula for I is not quite right.

 

[ryty]

thanks i figured it out, i accidently udes 30.33, not 33.33, and i found the right equation
I=.5mr^2, and the right answer is 7.5x10^-4, thanks for your help