10 kg Dumbbell?

Question

Imagine a lightweight, almost massless meterstick, with a 5 kg mass at each end (like a dumbbell). How much torque would be needed to give this object a rotational acceleration of 6 rad/s2 about its midpoint?

Answer 1

its momentum of inertia is J=2* 5*(0.5^2)=2.5
like F=m*a, C(torque)=J* dw(rotational acceleration)
so C=2,5*6=30 [N*m]

Answer 2

use this link

http://www.engineersedge.com/motors/calculator/accelerating_torque_force_general.htm