A 0.16 kg billiard ball moving to the right at 1.2 m/s has a head-on elastic collision with another ball of equal mass moving to the left at 0.85 m/s. The first ball moves to the left at 0.85 m/s after the collision. Find the total kinetic energy before and after the collision.

Suppose that three astronomical objects, 1, 2, and 3 are observed to lie on a line, and the distance from object 1 to object 3 is d. object 1 has four times the mass of object 3, and seven times the mass of object 2. find the distance between objects 1 and 2 for which the net force on object 2 is zero.