# Homework Help: Momentum of two balls collision question

1. May 23, 2010

### mvk1

Two balls of equal mass m undergo a collision. One ball is initially stationary. After the collision, the velocities of the balls make angles of 33° and 43° relative to the original direction of motion of the moving ball. If initial speed of moving ball is 5.4 m/s find the final speed.

What ive done:
In x axis:
M1V1+ M2V2= M1V1’+ M2V2’
M(5.4)+M(0)=M(V1’Cos33)+M(V2’Cos46)
5.4M= M( V1’Cos33+ V2’Cos46)
5.4= V1’Cos33+ V2’Cos46

In the y axis:
0= M1V1’+ M2V2’
0=M(V1’Sin33)-M(V2’Sin46)
(Dividing both sides by M)
0=( V1’Sin 33- V2’Sin46)
0= V1’Sin33- V2’Sin46

HERES IMAGE OF PROBLEM WITH DIAGRAM:
http://i.imgur.com/NKSeA.jpg

2. May 23, 2010

### Staff: Mentor

You have two equations and two unknowns. Solve them simultaneously. Try using the method of substitution. (Use one equation to express V1' in terms of V2'. Then substitute that into the second equation and solve for V2'.)

3. May 23, 2010

### mvk1

OMG THANKS YOU SO MUCH I DID IT RIGHT ON MY TEST!!!
PRETTY INTENSE BUT THANKS SO MUCH!!!!!
i found easier to use a,b for v1' and v2' made my life a lot easier