Average force applied by bullet

Click For Summary
The discussion centers on calculating the average force applied by a bullet given its mass and velocity. The equation F = ma is identified as the starting point, but there is confusion about how to determine acceleration. Participants question the need for additional data, such as the time of impact or the bullet's deceleration upon hitting the target. There is also uncertainty regarding the bullet's force while in flight, as it is not accelerating after being fired. Overall, the problem lacks sufficient information to arrive at a definitive answer.
joel amos
Messages
104
Reaction score
0

Homework Statement


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?


Homework Equations


F = ma


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?
 
Physics news on Phys.org
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.
 
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?
 
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.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
7
Views
1K
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
13
Views
7K