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Homework Help: Finding net torque

  1. Apr 17, 2005 #1
    I don't always pick up on little things in problems. In this particular problem, I am unsure of how to draw the picture when the car is rotated.
    Here is the problem:

    In San Francisco a very simple technique is used to turn around a cable car when it reaches the end of its route. The car rolls onto a turntable, which can rotate about a vertical axis through its center. Then, two people push perpendicularly on the car, one at each end, as in the drawing. The turntable is rotated one-half of a revolution to turn the car around. If the length of the car is 8.20 m and each person pushes with a 195-N force, what is the net torque applied to the car? (Use the randomzed force given in red above for your calculations, not the 185 N force labeled in the figure.)

    http://www.webassign.net/CJ/09_04.gif (That is the picture)

    I am confused about how to use the "one-half of a revolution turn" into the problem. I know that one revolution is 360 degrees, and a half is 180 degrees. Am I correct in making that statement based on the one-half of a revolution turn statement?

    Please help.
  2. jcsd
  3. Apr 17, 2005 #2
    That sounds like a correct assumption to me. Anyway, I think you'll want to find the radius of the circle, and the torque will just be FxR
  4. Apr 17, 2005 #3
    do you mean radius = 8.20 / 2 = 4.1
    and then 195 * 4.1? I did that and got a wrong answer. I think I am missing something that you are trying to tell me.

    Net torque.. so do I have to add those two forces * the radius?
  5. Apr 17, 2005 #4
    okay. dur. i got it.
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