# Homework Help: Calculating Net Torque of Uniform Disk

1. Mar 6, 2010

### copitlory8

The circular blade on a radial arm saw is turning at 265 rad/s at the instant the motor is turned off. In 12.0 s the speed of the blade is reduced to 85 rad/s. Assume the blade to be a uniform solid disk of radius 0.140 m and mass 0.400 kg. Find the net torque applied to the blade.

Relevant Equations:
Torque net = 0
Torque= F(r)
F=ma
angular accel. = w2r

Attempt:
$$\sum$$Torque=(.4)(265)2(.14)(.14) +(.4)(85)2(.14)(.14)
I known I need to sum the forces but I am unsure of what direction to use.