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How does a rotating wheel apply torque/force on a ball?

  1. Sep 20, 2012 #1
    I saw a baseball pitching machine that throws baseballs at 40-70mph with one wheel... All that wheel does is rotate and as the ball touches the rotating wheel it accelerates and comes flying out of the machine at an appropriate angle.. My question is: what is the physics behind that wheel on ball action? I understand torque but I don't get how it works since the ball is "parallel" to the wheel. There is nothing pushing the ball in a straight line... How is the energy transferred from wheel to ball??? Thanks!
  2. jcsd
  3. Sep 21, 2012 #2


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    Staff: Mentor

    The wheel moves quicker than the ball, and friction will accelerate the ball. The precise direction is not so important - after leaving the machine, the ball will always fly in a straight line (at least if we neglect gravity and air resistance), and if the direction does not fit, simply rotate the machine.
  4. Sep 21, 2012 #3
    there is friction between the ball and the wheel. It makes the ball move in the direction tangential to the point on the wheel where the ball makes contact.
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