Elastic Collisions - Understand Motion Transmission w/ Kinetic Energy

[luis20]

Hi everyone!

I'm new to this forum. I enjoy physics but I'm full of doubts :)

Now I'm trying to understand how motion is transmited through collisions and I can't understand why elastic collisions keep kinetic energy constant and why constant of restitution equals one.

I just imagine that the collision lasts until both corps have the same velocity. After that they keep their track without pushing each other. This is what makes sense to me, but I know I must be wrong.

Thanks for any help you can give :)
Luis

 

[nasu]

During the first part of the collision the two bodies are deformed (compressed). If the collision is elastic, they will expand back and their relative velocity will increase.
You can imagine a spring between the two rigid bodies. When one of them approaches the other, it will compress the spring until the relative speed of the two bodies is zero. But then the spring won't stay this way. If there is no elasticity, then you have what you describe in your post. That would be a plastic collision.

 

[luis20]

Thanks.

But I didn't understand well the part of the restitution.

Well, elastic collisions occur in all bodies that don't exceed their elastic limit during the collision right?

So, for instances, a elastic collision between a moving body and a stationary one. After they get deformed and reach the same velocity, the restitution begins.
They both expand toward each other. How do I know that in the first push of the restitution they don't finally separate and so all the velocity is not trasnmitted to the next body as it should be?
Cause the expansion of restitution as to accompany the increase of relative velocity between the bodies, so the transfer of velocity can be concluded. I hope you can understand my point.

I mean, I can expand a little bit, but during the time of that expansion, my increasing velocity gave me a greater distance between me and something that wasn't fullfilled by that expansion! So I couldn't remain in collision with that something.