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Calculating mutiple forces on a body

  1. Sep 7, 2012 #1
    I am making physics engine (computer) and i have some problems with interpretating multiple forces on one body.

    http://img837.imageshack.us/img837/396/75i7i47i6.png [Broken]

    On the fourth car (on right) there are two forces acting on two rear wheels, interpretation is obvious, but what when only one force is acting ? Which of these three interpretation, if any, is correct?
    How to calculate how much force is moving body and how much it is rotating it (moment) ?
    I currently use second image interpretation but i think it is not correct.

    And, second question, how to calculate when mutiple forces with random angles etc are present ?
    I think somebody asked that question before: https://www.physicsforums.com/showthread.php?t=222598
    but i don't understand answer he was given.
    I have force angles and forces, but i can have x and y components about any axis/angle. I need a way to calulate resultant force/moment.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 7, 2012 #2


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    2017 Award

    Staff: Mentor

    The total net force is always the (vector) sum of the individual forces, and you can sum all x-components for the x-component and all y-components for the y-component.
    The total net torque is always the sum of all individual torques, you can simply sum them.
    Diagram 2 looks good. Keep in mind that the rotation of a car is usually determined by the position of the wheels - external torque does not matter as long as the wheels do not slide.
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