Please help! An initially stationary 18-kg curling rock has a force applied to it over 2.0s. Its released with a velocity of 8.3 m/s [forward]. Determine the magnitude and direction of the applied force.

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.