Real life elastic collision and variation of kinetic energy

[velvetmist]

How small should $\Delta T$ be in a collision to be considered elastic? In elastic collisions $\Delta T =0$, but as far as I know, just atomic collisions are considered perfectly elastic. Then, which criterias are used to considere a collision between two objects elastic?

 

[Ibix]

It should be small enough that you don't care about the error from ignoring it for whatever your application is.

 

[velvetmist]

It should be small enough that you don't care about the error from ignoring it for whatever your application is.

I don't have any specific application. I was thinking in taking the percentage of $\Delta T$ from $T_i$, and if it's $<10\%$ it's acceptable, but I'm not sure if it could be a valid criteria.

 

[Ibix]

If you can tolerate an error of 10% in your energy measure, sure.

A purely elastic collision is an approximation to reality. There's no single answer to "how good does an approximation have to be to be useful" - it depends on how big the error is and how precise an answer you need.