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# common sense regarding the physical world

Nick George
Ranch Hand
Posts: 815
Say I have two perfectly circular "things" in an empty world. One has a mass of 2, the other has a mass of 1. Is there EVER an instance in which these two objects will collide, and the mass of 1 will have a resulting vector with a smaller magnitude than the mass of 2? This is occasionally happening in my program, which seems to me an indication that something's funky with my equations.

Warren Dew
blacksmith
Ranch Hand
Posts: 1332
2
Yes.

Consider the case where both objects are moving in the same direction on the same path, the more massive one at a speed of 1, and the smaller one behind it and overtaking it with a speed of 4. After the collision, conserving momentum and kinetic energy, the small object will be motionless, and the large object will have accelerated to a speed of 3. (Both before and after, total momentum is 6, total kinetic energy 9.)

Nick George
Ranch Hand
Posts: 815
But if the smaller mass is still, then should it always end with a greater velocity?

Warren Dew
blacksmith
Ranch Hand
Posts: 1332
2
By "Yes", I meant yes there is an instance in which these two objects will collide, and the mass of 1 will have a resulting vector with a smaller magnitude than the mass of 2 (in this example, the mass of 1 will have a resulting vector with a magnitude of 0).

fred rosenberger
lowercase baba
Bartender
Posts: 12127
30
Joeseph,

"If a 2kg object collides with a STATIONARY 1kg object, will the 1kg object ever have a smaller velocity?"

or, are you asking,

"a 1kg and 2kg object both have some initial non-zero velocity. is there some initial condition that will, after they collide, cause the 1kg object to have a smaller velocity than the 2kg?"

Arjun Shastry
Ranch Hand
Posts: 1898
1
Joseph,are they projectiles?or just moving on plane surface?

Nick George
Ranch Hand
Posts: 815
sorry, been away a month.

so, I've refined my physics a bit, but it still feels a bit off. Would it be possible to post a zip file anywhere, that some interested party could try out and tell me if i'm just being paranoid?