Help in collison equation?

Question

so the question is

each croquet ball in a set has a mass of .46 kg. the green ball, traveling at 13.4 m/s strikes the blue ball, which is at rest

assuming that the balls slide on a frictionless surface and all collisions are head on, find the final speed of the blue ball in each of the situation:

A) green stops moving after it strikes the blue ball. answer in m/s

b)the green ball continues moving after the collsion at 2.8 m/s in the same direction.. answer in m/s

c) green ball continues moving after the colision at .8 m/s in the same direction ... answer m/s

for the note i have the answer ... i just want to know how others do it .... im not giving the answer b.c then the mind of the solver changes .... thank you

Answer 1

ok...well the important thing to remember is that momentum is always conserved.  since each ball has the same mass, the problem will be significantly easier to solve.

so for the first one, if the green ball comes to rest, all the momentum must have been transfered to the blue ball.  that means the final speed of the blue ball is now the initial speed of the green ball: 13.4m/s

for part b, you just subtract the final speed of the green ball, 2.8m/s from the initial speed, 13.4m/s....the final speed of the blue ball is 10.6m/s

for c, just do the same thing...13.4-.8=5.4

hope i could help!