# Homework Help: Elastic collision help

1. Apr 9, 2009

### fball558

elastic collision help!!

1. The problem statement, all variables and given/known data

A spherical satellite of radius 4.7 m and mass M = 195 kg is originally moving with velocity
v1i = < 2800, 0, 0 > m/s, and is originally rotating with an angular speed w = 2 radians/second, in the direction shown in the diagram. A small piece of space junk of mass m = 4.1 kg is initially moving toward the satellite with velocity v2i = < -2200, 0, 0 > m/s. The space junk hits the edge of the satellite at location C as shown in the diagram, and moves off with a new velocity v2f= < -1200, 490, 0 > m/s. Both before and after the collision, the rotation of the space junk is negligible.

After the collision, what is the final momentum of the satellite?

What is the initial rotational angular momentum of the satellite, around location D (its center of mass)? (Be sure your signs are correct).

im stuck on these two parts. i found out the rest and now stuck.

i used Mv1i + mv2i = Mv1f + mv2f
but got stucked
what should i do? any help would be great!!
thanks

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2. Apr 9, 2009

### rl.bhat

Re: elastic collision help!!

It is not a head on collision. So you have to take the components of velocities of satellite and junk after collision to find the final velocity of satellite. You have to use the conservation of energy also.

3. Apr 9, 2009

### fball558

Re: elastic collision help!!

what do you mean by your first statement?
i know
inital velocity of sat. is 2800,0,0
inital velocity of junk is -2200,0,0
final velocity of junk is -1200,490,0
i found I (inertia) of the sat. and it is 1723.02
w was given in problem and is = 2 r/s
energy wise you have translational KE of the sat and of the junk. also the sat has rotational KE
i found the total kinetic energy of the system to be 774330615.1 J
but i dont know what to do with these numbers to find P of sat.
is there an equation or something?