Two boys weighing 60 N and 70 N sit on a see-saw. The boy weighing 60 N sits on the left side of a seesaw at a distance of 1m from the pivot while the other boy sits on the right side at a distance of 1.2 m. What distance must a third boy of weight 80 N sit on the left side in order to balance the see-saw?

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.