1. ball a, with a mass of 20 kilograms, is moving to the right at 20 meters per second. at what velocity should ball b, with a mass of 40 kilograms, move so they both come to a standstill upon collision? identify each mass, velocity, and unknown. show your work, including units, and indicate the direction of ball b in your answer.

2. ball c, with a mass of 30 kilograms, is moving to the left at 10 meters per second. at what velocity should ball d, with a mass of 10 kilograms, move to the right and collide with ball c so that ball d rebounds to the left with a velocity of 30 meters per second and ball c rebounds to the right with a velocity of 10 meters per second? assume the collision to be perfectly elastic. identify each mass, velocity, and unknown. show your work, including units, and indicate the direction of ball d in your answer.

3. ball e, with a mass of 10 kilograms, is moving to the right at 20 meters per second. ball f is moving to the left at 20 meters per second. upon collision, ball f comes to a standstill and ball e moves to the left at twice its original speed. what is the mass of ball f? identify each mass, velocity, and unknown. show your work, including units.
(show your work on all of them, )