# Homework Help: Rotation with a Pulley and Masses

1. Mar 16, 2005

### BlasterV

one block has a mass M = 500 g, the other has mass m = 460 g, and the pulley, which is mounted in horizontal frictionless bearings, has a radius of 5.00 cm. When released from rest, the heavier block falls 85.5 cm in 2.47 s (without the cord slipping on the pulley).

First I did conversions:
M = .5kg, m = .46 kg, r = .05 m
fall = .855m in 2.47 s

I am unable to do part b and c right, so I am unable to go further.
Here is my work:

.855m = 1/2 a (2.47^2) a = .28 m/s^2

however, It asks for 2 tensions. I never learned how to seperate them like that, especially with a pulley. I did:

9.8 m/s^2 * .5kg = 4.9 N
9.8 m/s^2 * .46kg = 4.508 N

Tension of Cord = 4.9N + 4.508N. Obviously this isn't right, where do I go from here, or did I miss something?

(a) What is the magnitude of the block's acceleration?
.28 m/s2
(b) What is the tension in the part of the cord that supports the heavier block?
N
(c) What is the tension in the part of the cord that supports the lighter block?
N
(d) What is the magnitude of the pulley's angular acceleration?