# Law of conservation of energy and momentum

1. Nov 18, 2009

### yomama

Two Objects collide head on, both with speeds of 10 m/s. Both projects emerge from the collision traveling in the same direction, each having at a speed 10m/s.

How does this violate the conservation of momentum?

That it only violates the conservation of momentum.
Why?

I answered it as violating both conservation laws (momentum and energy), because I thought any force that was applied on one twice is applied on the other. And also because both objects would not emerge from the direction because they are both traveling at the same speed.

2. Nov 19, 2009

### SeanGillespie

The total momentum before a collision must equal the total momentum after a collision.

Before the collision, both are travelling towards each other at 10m/s... As momentum is a vector quantity it will have a direction; you can say that object A = 10 m/s, while object B = -10 m/s. The "system" is therefore balanced and the total momentum is equal to zero...

Bearing in mind that they are travelling in the same direction after the collision, be it in the positive or negative direction, what would be the total momentum of the system?
Does this total equal the same as the total before the collision and is it therefore conserved?