# Collision Reaction

## Main Question or Discussion Point

Hello,
I have a question about how balls react on collision while having diffrent mass,
lets say two balls are moving on one dimension, the first ball has the speed of V1, mass of M1, and the other ball has V2,M2.
what will be their speed after the collision?
assuming there are no other forces involved.
It is logical to me that if their mass is the same, the balls will exchange their speed, but I don't know what will happen if the balls will be with diffrent mass.

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Hootenanny
Staff Emeritus
Gold Member

If one assumes that the collision is completely elastic then both momentum and kinetic energy are conserved and the problem can be solved.

If one assumes that the collision is completely inelastic then just momentum is conserved and the problem can be solved.

In the case where neither of the above apply then the problem cannot be solved without further information.

Thanks you solved all my problems :)

Shooting Star
Homework Helper
It is logical to me that if their mass is the same, the balls will exchange their speed, but I don't know what will happen if the balls will be with diffrent mass.
I am just curious to know on what you based this conclusion, because you didn't mention anything about the co-eff of restitution or consvn of KE.

Last edited:
I didn't mention "co-eff of restitution or consvn of KE" because I don't know what any of those means, I don't know much about physics, I'm a programmer and just wanted to build a physics engine for a project I have. That conclusion was based on intuition only.

Shooting Star
Homework Helper
Hootenanny has replied to you qualitatively, without going into any math. Could you really understand everything about collision of balls from that?

(Please ignore this post if you feel that it is not productive for you to continue with this discussion.)