# PHYSICS HELP

posted by PHYSICS HELP

A disk has a moment of inertia of 3.0x10^-4 and rotates with an angular speed of 3.5 rad/sec. WHat net torque must be applied to bring it to rest in 3.0s? can some one help me out with this im lost!!!

1. Glenn

Torque is equal to the change in angular momentum divided by the change in time. Initial angular momentum is equal to the rotational inertia times the angular speed. Final angular momentum is zero because it stopped.

Hope this helps!

2. natali

so is this right ?

i get 3.5x10^-4 N.m is this correct?

3. bobpursley

Yes

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