Physics 203
posted by Kayla on .
A 4 kg block resting on a frictionless horizontal ledge is attached to a string that passes over a pulley and is attached to a hanging 2 kg block. The pulley is a uniform disk of radius 13.0 cm and mass 0.50 kg.
(a) Find the speed of the 2 kg block after it falls from rest a distance of 2.5 m.
(b) If an additional 5.0 mJ of energy are supplied to the rotational energy, what is the new angular speed of the ball?

look at the energy change:
change in PE=change in KE
2*g*2.5=1/2 (4+2)v^2 + 1/2 I w^2
where I is the moment of inertia for a pulley ( I would model it as a solid disk)
now to relate w to v, remember w=v/r
b) makes no sense to me.