# Average force applied by bullet

1. Oct 24, 2012

### joel amos

1. The problem statement, all variables and given/known data
What is the average force applied by a 75 g bullet that leaves a gun at 1350 m/s and hits a target 75m from the barrel of the gun?

2. Relevant equations
F = ma

3. The attempt at a solution
First I had the equation F = ma, and began filling in all the variables I could. In this case, I only started with the mass. As for acceleration, I don't know how to find it. Could I rearrange Vf^2 = Vi^2 + 2ax to solve for a? If so, what's the final and initial velocity?

2. Oct 24, 2012

### haruspex

The question makes little sense to me. Average force over what time? The time from reaching the target to coming to rest? How long is that?? You could determine the average over the time from leaving the barrel to being embedded in the target, but that seems a strange thing to ask for.
Please confirm you have represented the question accurately.

3. Oct 24, 2012

### joel amos

The question is as posted. It did seem quite strange to me too. But since the bullet is no longer accelerating after its fired, how can it have a force?

4. Oct 25, 2012

### PhanthomJay

Something is missing in the problem statement. In flight, neglecting air resistance, the bullet exerts a small gravitational force on the earth and nothing more, until such time as it embeds into the target with a substantial force, but you don't give any more data which is necessary to determine what this force might be.