# Collisions question

1. Nov 22, 2006

### student85

This might be stupid but I was thinking, when two subatomic particles collide at very high speeds, they form a bigger particle whose mass is less than the sum of the smaller ones, and the mass lost transforms into energy as in Einstein´s equation E=mc2.
What happens with non subatomic particles, say two balls colliding or whatever. Is there a mass loss that turns into energy. THIS SOUNDS VERY OFF LOL, because the amount of energy released with just a little bit of mass is huge. But then, what is wrong here? Why doesn't this happen, or if it does, why isn't it percieved?

2. Nov 22, 2006

### Danger

There isn't a mass loss, unless you count something like little pieces chipping off. The energy lost through macroscopic collisions is primarily in the forms of heat and sound. You would get mass loss only if the materials were such that a chemical or atomic reaction occurred when they hit.

3. Nov 22, 2006

### cesiumfrog

There should be a mass loss. The approaching balls are heavier than they would be if they were at rest (KE=(m-m0)c2), and after the collision (assuming some energy is lost to sound etc) there will be slightly less total kinetic energy (because some of the mass-energy has been transfered into air-vibrations, perhaps some even radiated away as a flash of light, etc).

Similarly, 2xH2O should not weigh the same as 2xH2 + O2.

4. Nov 23, 2006

### student85

Thanks danger and cesiumfrog, you really helped me!

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