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Homework Help: Determine work in circular motion

  1. Mar 25, 2015 #1
    1. The problem statement, all variables and given/known data
    An object, moving along the circumference of a circle with radius ##R##, is acted upon by a force of constant magnitude F. The force is directed at all times at a ## 30 \degrees ## angle with respect to the tangent to the circle. Determine the work done by this force when the object moves along the half circle from A to B.

    2. Relevant equations

    3. The attempt at a solution
    My solutions guide tells me to us ##\int (Fcos \theta dl)## The question stated "constant force", so why do we need to integrate? Why can't I use F dot D?

    Thank you!

    By the way, how do I write in limits for integration?
  2. jcsd
  3. Mar 25, 2015 #2


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    limits for integration: _lower ^upper , i.e. subscript, superscript . Degrees: ^\circ

    F is not constant. Its magnitude is constant.

    What do you mean by D ? "Why can't I use F dot D"
    Last edited: Mar 25, 2015
  4. Mar 25, 2015 #3


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    If by D you mean the distance element vector ##\vec {dl}## then ##F \cos(\theta)dl = \vec F . \vec D##.
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