# Find the net torque on the pulley

## Homework Statement

The pulley in the figure has radius 13.0 cm and a moment of inertia 0.230 kg m^2; the pulley is constructed from a dense metal. The rope does not slip on the pulley rim. The system is released from rest.

http://session.masteringphysics.com/problemAsset/1000057320/10/YF-09-36.jpg

Find the net torque on the pulley, about its axle, due to the differing tensions in the rope on the two sides of the pulley.

## The Attempt at a Solution

From earlier parts of the problem i have found the acceleration of the blocks a = 1.0m/s^2 and the velocity final of the larger falling block v = 3.16 m/s. i also found the tension in both of the ropes. T in rope attached to the larger mass was 35.2 N and the T in the rope on the smaller mass was 21.6 N

Now i cannot find the net torque it is asking for

I tried doing this

t = torque

tlarger block - tsmaller block = tnet

T*d - T*d = tnet

35.2N(5m) - 21.6N(5m) = tnet

tnet = 68Nm

This is wrong? How else can i go about this problem?

thank you

## Answers and Replies

i was using the height instead of the radius

i got it now :)