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Torque/Static Equilibrium Problems

  1. Feb 21, 2007 #1
    1. The problem statement, all variables and given/known data:
    I have 2 problems:
    1. We have a stick of length 30cm. The stick has a pivot point in its left end. We have a force 3.3N acting at angle 0.7rads and a distance 16.1cm from the pivot. What is the MAGNITUDE of the force we must apply perpendicular to the stick at a distance 5.0cm from the pivot so that the stick does NOT rotate?

    2.I am applying a force 2.4N on a wrench at an angle 0.5rads from the horizontal. If the point of application of the force is 7.8cm from the pivot, what is the MAGNITUDE of the torque about the pivot?

    2. Relevant equations:
    Torque = Force * Perpendicular Distance
    Perpendicualr Distance = distance * sin(theta)
    Note: I'm not sure if it matters in problem one that the distances aren't the end of the object.

    3. The attempt at a solution:
    Torque1 +Torque2 = 0
    Torque1 = .161 m * (3.3 N) * (sin (.7)) = 3.422
    Torque2 = -3.422 = F(.5)(sin (pi/2)) = .5F
    -6.844 = F
    Mag. F = 6.844 N

    2.Perpendicular Distance = .078 m * sin(.5) = .037
    Torque = 2.4 N * .037 m= .09 Nm
  2. jcsd
  3. Feb 22, 2007 #2


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    I'm not sure why you used the sine here, since the distance is perpendicular? Or am I missing something?
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