An adult and a small child are sitting at locations on a massless seesaw so that it is balanced and horizontal. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw? Assume that both people are small enough compared to the length of the seesaw to be thought of as point masses.

The seesaw will still be in stable equilibrium, in that when they move it will return to it balanced horizontal position.

Explanation:

From my analysis of this problem. Both the adult and the child where balanced seated at their respective distance from the pivot, so long as they moved equal distance(one half their original distance) from the pivot, their individual moments about the pivot will remain unchanged, so that the seesaw remains balanced as before.

What is moment?

Moment is a turning effect of a force about a point from a point of action

Moment=force x perpendicular

distance

Principles of moment state that

1. Sum of anticlockwise moments equal sum of clockwise moments

2. Sum of upward forces equals sum of downward forces

increases it

no. dot product   =0 when vecs at right angles