[alex_ferguson]

I need help with the following questions:

A 3kg ball is at rest. A 2kg ball, moving at 3 m/s, collides with it. The balls do not stick together, they move off separately. There is no friction or rolling.


1.

a. What is the initial momentum of the 2kg ball?
b. If the 3kg ball moves off with a velocity of 1 m/s, calculate the momentum of this ball
c. State the combined momentum of the 2 spheres after they collide
d. Calculate the velocity of the 2kg ball after the collision
e. Calculate the initial kinetic energy of the 2kg ball
f. Calculate the final combined kinetic energy of the two balls

[Capuchin]

Hi Alex

I don't want to give too much away, as the questions are simple, and I'm sure you have all the know-how you need to answer.

Just remember that the momentum p = mv
and that momentum within a closed system is constant, that is to say that the combined momentum of both balls before the collision is equal to the combined momentum of both balls after collision.

draw a diagram for before and after collision, work out m and v for each ball before and after from what you're given, then you should be able to work out the other values from the information I have given you.

Kinetic energy KE = 1/2mv^2, so once you have the information above, you can work that out too.

Good luck, if you have any problems be sure to reply.