A 1-kg mass hangs by a string from a disk with radius 5.1 cm which has a rotational inertia of 5 × 10-5 kg•m2. After it falls a distance of 1.4 meters, how fast is it going?

Question

What is the angular velocity of the disk?

Answer 1

Is the string wound around the disc, so that the disc spins when the weight falls?

If so, then use

M g H = (1/2)M V^2 + (1/2) I*(V/R)^2

to solve for V, the velocity when H = 1.4 m.

The second term on the right is the disc's rotational kinetic energy. V/R is the angular velocity that they want.

Answer 2

Thanks a lot