# Math Help - Maximum torque problem

1. ## Maximum torque problem

Hi all,
Can anyone help with this problem from my statics revision? It's the only one from my worksheet I am struggling with.

A solid steel shaft has a diameter of 60mm. Determine the maximum torque that can be applied to the shaft if the maximum twist per meter is to be 1 degree. The shaft has a shear modulus of 80 GPa.

I don't seem to have anything in my notes that would help me tackle this problem.

MM

2. ## I think I have worked the solution

If anyone can see something I have done wrong then please let me know.

Diameter = 60mm = 0.06m
Length = 1m
Theta = 1 degree = 0.0175rads
Shear modulus = 80 x 10exp9

Torque = G*r*theta/L
Torque = 80 x 10exp9*0.03*0.0175/1
Torque = 42000000
Torque = 42kNm

I think I have answered my own question. Just thought I'd post the answer I got.

MM

3. Hello
Originally Posted by marky001
If anyone can see something I have done wrong then please let me know.

Diameter = 60mm = 0.06m
The only thing I can say is that $\frac{G r \theta }{L}$ can't be a torque since it's unit is Pa.radians=N.rad/m^2 which is quite different from N.m.