# Conservation of Momentum of cannonballs

1. Apr 6, 2009

### okgo

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

You are shooting cannonballs from a cannon. To achieve the maximum range of the ball, would you be better off fastening the cannon to the ground or letting it be free to recoil, or wouldn't it matter? Explain your reasoning

2. Relevant equations

Conservation of momentum

3. The attempt at a solution
Like in a gun, there is a recoil, but since the gun has a larger mass than the bullet, its velocity is less.

But I don't think it would matter if the cannon was fasten to the ground because wouldn't the recoil of the cannon would be transferred to the bolts and ground, therefore the cannonball would still fire at maximum range?

2. Apr 6, 2009

### LowlyPion

Consider 2 cases. One you have 2 blocks in space with a spring that pops them in opposite directions. In that case from Newton's Third Law won't each get half the energy as each pushes against the other equally? The center of mass stays the same. The second case is a block pushed by a spring from against a wall. Same PE in the spring. Which gets more kinetic energy?