Max shearing stress problem

  1. Hey guys, I got a problem that goes like: A shaft with a circular cross section is subjected to a torque of 120ft-lb. Its shaft's diameter is 0.750 in and its length is 15 in., determine the maximum shearing stress.

    I did the following: I tried to use shearing stress = Tr/J in which i plugged in as followed (120*.750/2)/(pi/32)*.750^4 and i get 1448, but the answer should be17.39ksi. I assume i am not getting the right answer because I am not factoring in the length but I am not sure. Any help is appreciated, thanks
  2. jcsd
  3. nm, i figured it out, Stupid me forgot to convert the ft-lb to inch-lb.
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