Final velocities from head elastic head on collisions

[henry3369]

Homework Statement

Ball A with velocity +3.00 m/s collides with ball B with equal mass traveling at -2.00 m/s. What is the velocity of each ball after the collision.

Homework Equations

Not sure.

The Attempt at a Solution

I know that momentum is conserved because, but solving the conservation of momentum equation yields two unknowns. I also tried impulse-momentum theorem and conservation of kinetic energy, but I'm not sure how that will help. The answer is Ball has velocity -2.00 m/s and ball B has velocity +3.00 m/s. Is there a formula to actually solve for this because they don't give you either of the final velocities.

 

[Maged Saeed]

How did you use the law of conservation of kinetic energy?

 

[Maged Saeed]

If you can put one of the velocities of the balls after the collision in term of the other , you can solve this problem.
And the law of conservation of kinetic energy would help you.

 

[henry3369]

If you can put one of the velocities of the balls after the collision in term of the other , you can solve this problem.
And the law of conservation of kinetic energy would help you.

Well in my book they gave me a formula for relative velocity which is V_2f-V_1f = -(V_2i-V_1i). And I have the initial velocities and which will leave me with two unknowns still. Do I have to relate this somehow to conservation of kinetic energy and solve simultaneous equations?

 

[henry3369]

Ahh I got it. Thank you!