A125g steel ball with a kinetic energy of .25j rolls along a horizontal track how high up an inclined track will the ball roll if friction can be ignored

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?

Amoving electron has kinetic energy k1. after a net amount of work w has been done on it, the electron is moving one-quarter as fast in the opposite direction. (a) find w in terms of k1. (b) does your answer depend on the final direction of the electron's motion?