Calculating Final Speed in Elastic collision (momentum)

[Mushroom79]

Homework Statement

If it is eg. two balls, both going to the right before and after an elastic shock, how do you determine their velocities after the collision? (speeds before and weights are given)

Eg.

M = 50 kg
u1 = 20 m / sm = 100 kg
v1 = 10 m / s

(M, m = mass)
(u1, v1 = velocity before the collision)
(u2, v2 = velocity after collision)

Homework Equations

The law of conservation of momentum:
m*v1+M*u1= m+M*v2*u2

Momentum before = Momentum after

The Attempt at a Solution

m*v1+M*u1= m+M*v2*u2 →

100 * 10 +50 * 20 = 100 +50 * v2 * u2

How do I continue from here?

 

[ZxcvbnM2000]

In elastic collisions energy is also conserved , so you can set up one more equation .

 

[Mushroom79]

In elastic collisions energy is also conserved , so you can set up one more equation .

Oh, right. Think "momentum before equals momentum after" is what you meant.
Forgot to put it there.

 

[ZxcvbnM2000]

In elastic collisions :

Momentum is conserved

Energy Is conserved
In inelastic collisions:

Momentum Is conserved

Energy is not conserved

Just to be more clear :P