Using the principle of moments to determine distances and forces when rotational forces are balanced. "For example, imagine Sam slides backwards along the seesaw shown above until it balances. We know the moment of Sam's force must now be the same as that of Caitlin's, i.e. 600 N m, because they balance. Sam's weight hasn't changed, so we can rearrange the equation for the moment of a force to calculate his new distance from the pivot:"