# Solid/rigid bounce

1. Nov 21, 2013

### magmash

Hi guys

enlighten me, How can Rigid bodies with smooth surfaces bounce in a collision

An example is, drooping a metal sphere on a metal surface

is there any deformation happening here as in the situation of a basketball ?

2. Nov 21, 2013

### Simon Bridge

Deformation - yep.
There is no such thing as the classically rigid body - everything deforms.

3. Nov 21, 2013

### TumblingDice

One artifact of deformation would be the sound waves you hear when the ball meets the floor. As Simon said, there's no such thing as an absolutely rigid object. The atoms and molecules will 'absorb' the energy, and react according to their composite structure.

4. Nov 21, 2013

### Staff: Mentor

Metal balls are not rigid (and nothing truly is completely rigid). They are very elastic.

Last edited: Nov 21, 2013
5. Nov 22, 2013

### magmash

so speaking in simple terms, there is nothing purely rigid in this world every thing deforms during a collision, and that is what is responsible for the bouncing effect that we can observe, am i right ?

P.S

Is it possible to observe the deformation of an very rigid/solid object during a collision ?

6. Nov 22, 2013

### Simon Bridge

That is correct.
Is it so hard to believe that the real world is messier than our idealized models?

Define "very solid" and "object" - but, in principle, yes.
For macroscopic objects you need to use interference techniques - but, as TumblingDice said, the sound of the objects striking is a result of the deformation.

If the objects did not deform, then the collision would take place in zero time ... giving "end of the Universe" type issues.

7. Nov 22, 2013

### magmash

Lets assume that we have a stone and a surface that don't deform, would dropping the stone down on the surface not result in any sound ?

I appreciate your kind responds : )

8. Nov 22, 2013

### Simon Bridge

How does sound happen?

However, for a collision of two classically rigid surfaces there are other issues like the zero time change in momentum.
If two rigid balls bounce off each other... What happened in terms of the force each experienced?