# Homework Help: Online Physics HW~Elastic Collision

1. Nov 27, 2008

### greenpak07

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

Hi guys,
Im a bit stumped on how to solve an online physics homework problem on elastic collision and it's really bothering me since we haven't gone over it in my class and all I have to help me is the book. I have no idea how to come up with the angles or even attempt the problem and neither do my friends. We'd all really appreciate it if someone could help us.
Many Thanks,
Pooja

A proton, moving with a velocity of vi, collides elastically with another proton that is initially at rest. Assuming that after the collision the speed of the initially moving proton is 2.00 times the speed of the initially at rest proton, find the following.
(a) the speed of each proton after the collision in terms of vi
initially moving proton _________multiplied by vi
initially at rest proton _______multiplied by vi

(b) the direction of the velocity vectors after the collision
initially moving proton __° relative to the +x direction
initially at rest proton __° relative to the +x direction

2. Relevant equations
K1=1/2m1vi^2
K2=1/2m2vi^2

3. The attempt at a solution

2. Nov 27, 2008

### Staff: Mentor

What vector quantity is conserved in any collision? For elastic collisions, what else is conserved?

3. Nov 27, 2008

### greenpak07

Hi,
I'm not sure but I'm going to say velocity?