Question

(part 1 of 3) Each croquet ball in a set has a mass of 0.54 kg. The green ball, traveling at 14.4 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 following situations: a) The green ball stops moving after it strikes the blue ball. Answer in units of m/s.

(part 2 of 3) b) The green ball continues moving after the collision at 2.5 m/s in the same direction. Answer in units of m/s.

(part 3 of 3) c) The green ball continues moving after the collision at 0.6 m/s in the same direction. Answer in units of m/s.

Answer 1

apply momentum conservation in each situation

case 1)  

Pinitial = Pfinal

Pgreen+ Pblue initial =Pgreen+ Pblue final

0.54*14.4 +0.54*0 ( at rest so u=0) = 0.54*0 +0.54*Vblue

Vblue = 0.54*14.4 /0.54 = 14.4 m/s answer

case2

Pgreen+ Pblue initial =Pgreen+ Pblue final

0.54*14.4+ 0.54*0 = 0.54*2.5 +0.54*Vblue

Vblue = ( 0.54*14.4-  0.54*2.5) /0.54 = 11.9 m/s answer

case3

Pgreen+ Pblue initial =Pgreen+ Pblue final

0.54*14.4+ 0.54*0 = 0.54*0.6 +0.54*Vblue

Vblue = ( 0.54*14.4-  0.54*0.6) /0.54 =13.8 m/s answer