# Homework Help: Conservation Of Momentum

1. Feb 23, 2012

### anthonych414

1. The problem statement, all variables and given/known data

In an explosion the two identical trolleys, each of mass m, were initially at rest. Find the total
momentum of the trolleys after the explosion.

2. Relevant equations

Conservation of momentum.

3. The attempt at a solution

Well, I assumed both trolleys to be particles in 2D-motion, and since they have the same mass and were both subjected to the same explosion, and thus were given the same acceleration, the total momentum should be zero. But, a friend of mine said that it could not be determined from the given. Who's right?

2. Feb 23, 2012

### Staff: Mentor

what is the total momentum of the system ie both trolleys BEFORE the explosion?

conservation of momentum says it must be the same afterwards.

Since you know the systems momentum before then you know it after. The explosion causes the trolleys to fly apart at the same speed since they are identical but in opposite directions. total momentum = mtrolley * V + mtrolley * (-V) = 0