• Question: Can static friction do work on an object?

    Asked by Harry to Daniel, Hannah, Maggie, Ry, Scott on 14 Nov 2017.
    • Photo: Ry Cutter

      Ry Cutter answered on 14 Nov 2017:

      Sometimes friction works against gravity (imagine car using breaks on hill). This means even though nothing is moving friction is still working!
      If you’re using the classic definition of work however, which is work = force times distance (W= F x d) if the friction is static then there is no work being done! This is because there is no distance being traveled!
      Great Question,
      Ryan

    • Photo: Maggie Lieu

      Maggie Lieu answered on 14 Nov 2017:

      Work done is the force times distance. Static friction means you don’t travel any distance so the work is zero.

    • Photo: Scott Melville

      Scott Melville answered on 14 Nov 2017:

      So if the object doesn’t have any size, I think Maggie is spot on. But imagine you had a big squishy object, with one side resting against a surface. Then static friction can certainly do work, because this classic formula that Ryan mentions involves the distance traveled by the Center of Mass – so if the center of mass moves while one of the sides stays still (and experiences the static friction), then work is being done!
      So I guess the answer is something like: “sometimes”. Usually it doesn’t do any work, because if a body is rigid and nothing is moving then no work is happening. But you can always cook up some silly example where a squishy body experiences both static friction and work, so I guess in those cases it does 🙂

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