posted by sandhya .
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?
What is the angular velocity of the disk?
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.
Thanks a lot