Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Torque and equilibrium; concept problem

  1. Dec 2, 2008 #1
    1. The problem statement, all variables and given/known data

    I'm just trying to understand why the force from net torque isn't included in net force when considering equilibrium: Why isn't the force from torque part of the net forces acting on a body?

    2. Relevant equations
    if net force = 0 and net torque = 0 then the body is in equilibrium;
    net force = ma, torque = Frsin@, where @ is theta

    3. The attempt at a solution
    It seems like the force required for torque should be part of the net forces acting on the body.
  2. jcsd
  3. Dec 2, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    "Net force" is not a force, it's the sum of individual forces. You can certainly have forces acting on something so as to create a net torque, yet those same forces add up to zero net force. For example: a vertical force to the right of center and an equal but opposite vertical force to the left of center.

    And you can also have a net force on a body with zero net torque.
  4. Dec 2, 2008 #3

    Your example helped me:

    So from this I now believe that the force from the torque actually is considered in the net force acting on the object. Now I am starting to understand why both net force and net torque need to be included for equilibrium.
    Last edited: Dec 2, 2008
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook