Question

A disk with a rotational inertia of 7 kgm^2 rotates like a merry-go-round while undergoing a torque given by (5+2t)Nm. At time 1s, its angular momentum is 5kg m^2/s. what is its angular momentum at 3s?

I can't figure out how to start this problem.

Answer 1

angular momentum change is the integral of torque, which is a time-dependent functiuon in this case.

(I*w)@t=3s - (I*w)@t=1s
= Integral (5 + 2t) dt
t = 1 to t = 3
= 5*(3-1) + (3^2 - 1^2)
= 10 + 8 = 18
Add 5 (the initial angualr momentum) to that for the angular momentum at 3 s.

Answer 2

Thank you