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Sample Problem 1: One mass on a See-Saw

A 3.0kg mass is place 2.00m to the right of the pivot point of a see-saw. What is the the magnitude and the sign of the torque applied?
 

This problem looks like the figure

The force exerted by the mass is due to gravity and is found from F=mg. The distance between the force and the pivot point is r=2.00m. We can find the magnitude of the torque by


If the mass is to the right of the pivot point, the rotation will be in a clockwise direction, so the torque is negative: .  As always, note the use of significant figures.  The distance r was given to three significant figures, but the mass (and therefore the force) is only known to two significant figures.  Thus the torque must have only two significant figures.  For more knowledge, visit the significant figures review


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