Question

A school yard teeter totter with a total length of 5.46 m and a mass of 35.9 kg is pivoted at its center. A 17.7 kg child sits on one end of the teeter totter. Where should a parent push with a force of 272 N in order to hold the teeter totter level?

Answer 1

sum moments about the center.

5.46/2 * 17.7g-272N*d=0 the sum of moments about any point equals zero. d is the distance away from the child, on the opposide side.

Answer 2

Since the board is balanced at the center, the weight of the board does not contribute a moment.

You must balance the moment (force x distance) applied by the parent with the moment due to the weight of the child.

272*X = (17.7 kg)*g*(2.73 m)

Solve for X in meters

Note that the child's mass has to be multiplied by g to get the weight force in Newtons.