I have this number where they give me the coordinates of 3 particles and the mass of each one of them. Afterwards, there's a force applied on 2 of those particles and they ask me to calculate the systems total moment of inertia. But then they ask me this:

Question

If the system goes from rest and that the forces from c) are applied for 5 seconds and after that 5 seconds no more forces are exerted, how much time does the system take to perform one full rotation.

So I think I'll find the answer using
T = 2pie/w, where I'll find w by first finding my angular acceleration a = t/I
from where I can find w using w = at. Then I solve for T in the first one.

is that correct?

Answer 1

Calculate I total for the three particles
(I = sum of 1/2 m r^2 for all three).

Then sum torques=I * angacceleration
solve for ang acceleration.

displacement=1/2 * angacceleration*time+wi*t

where wi=angacceleartion*5sec
solve for time from the displacement equation.

Answer 2

thanks bob!