Physics Help

[TheMan123]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w06_qp_1.pdf

Could someone help me out with Q11?
I know that its either A or D because the momentum before= the momentum after, but the answer is D, can anyone explain why???

 

[ismailmz]

In elastics collision momentum and kinetic energy is conserved, so when the left ball hits with the velocity the ball transfers its velocity to the other ball, which means K.E is being conserved. well this means the left ball stops and the right ball gains velocity and starts to move.

 

[TheMan123]

In elastics collision momentum and kinetic energy is conserved, so when the left ball hits with the velocity the ball transfers its velocity to the other ball, which means K.E is being conserved. well this means the left ball stops and the right ball gains velocity and starts to move.

Oh thx for that I get it now.
Correct me if I'm wrong, A is wrong because in A, kinetic energy is not conserved as total Kinetic Energy after the collision becomes half of its original, but in D it is conserved

 

[ismailmz]

exactly