# Which solution is correct?

1. Dec 22, 2011

### pantheid

I'm trying to plug in negative mass into conservation of momentum and energy equations. I want to see what would happen if a -1kg ball traveling at 1m/s smacks into a 2kg ball in an elastic collision. If the second ball is 1kg, then it remains stationary while the negative ball continues to travel at 1m/s, like they didn't even interact. If its 2kg, I get 2 answers for the speed of the positive ball, zero and negative two. How do I know which is correct?

2. Dec 23, 2011

### sophiecentaur

If you try to apply Maths to a non real problem then you will not get an answer that has no meaning in the real world. Your Maths will give you a correct Mathematical answer if you make all the steps correctly but, as with Computers, GIGO.

3. Dec 23, 2011

### pantheid

I believe there is a proof that newtonian mechanics hold for negative masses. It can be found on the wikipedia page for negative mass, so technically its not garbage.

4. Dec 23, 2011

### DrewD

The best way to find out is with an experiment, but that is not an option. I have never heard of negative mass being used in Newtonian Mechanics, and most of the time when negative mass comes up in other areas of physics, it predicts things that have never been observed. That doesn't mean that it doesn't exist, but you might be better off researching different topics.