Torque Problem, need to verify answer

[silvashadow]

Homework Statement

The circular blade on a radial arm saw is turning at 262 rad/s at the instant the motor is turned off. In 18.0 s the speed of the blade is reduced to 85 rad/s. Assume the blade to be a uniform solid disk of radius 0.130 m and mass 0.400 kg. Find the net torque applied to the blade.

Homework Equations

Sum torque=moment of inertia X angular deceleration

The Attempt at a Solution

ΣT=Ia
a=(Wf-Wi)/t=(85-262)/18=-10 rad/s
ΣT=.5mr^2*a
=.5*.4(.13)^2*10 = .0338 Nm

 

[Anadyne]

I think the moment of inertia for a uniform solid disk is 1/2*m*r^2.

 

[silvashadow]

I think the moment of inertia for a uniform solid disk is 1/2*m*r^2.

my bad, changed.

 

[Anadyne]

I don't see anything else wrong... but I could be wrong. ^^;