A playground merry-go-round has a radius 2.40 m and a moment of inertia 2100 kgm^2 about a vertical axle through its center, and it turns with negligible friction.
A child applies an 18.0 N force tangential to the edge of the merry-go-round for 15.0 s. If the merry-go-round is initially at rest, what is its angular speed after this 15.0 s interval?
[tex]\vec \tau = \vec r \times \vec F[/tex]
The Attempt at a Solution
I have absolutely no idea what to do. I know the answer is .309 rad/s. From playing around with the numbers I know that (2.40 m * 18.0 N * 15.0 s)/2100 kg*m^2 = 0.309 rad/s, but I don't know why. I can't find any sort of relationship between what I have and what I need.