Force Needed to Stop a Flying Bullet

  • Thread starter IBdoomed
  • Start date
  • #1
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A bullet of mass 0.0025 kg moving at 470 m/s
impacts a large fixed block of wood and travels
6.2 cm before coming to rest.
Assuming that the deceleration of the bullet
is constant, find the force exerted by the wood
on the bullet.
Answer in units of kN

I know force= mass * acceleration but i don't know how the distance plays into the solution. Any kind of kinematics formula would be sufficiently helpful!
 

Answers and Replies

  • #2
PeterO
Homework Helper
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48
A bullet of mass 0.0025 kg moving at 470 m/s
impacts a large fixed block of wood and travels
6.2 cm before coming to rest.
Assuming that the deceleration of the bullet
is constant, find the force exerted by the wood
on the bullet.
Answer in units of kN

I know force= mass * acceleration but i don't know how the distance plays into the solution. Any kind of kinematics formula would be sufficiently helpful!
Choose wisely from the sets of equations shown in the first two sections of this wikipedia posting.

http://en.wikipedia.org/wiki/Equations_of_motion
 
  • #3
16
0
i was trying to use v^2= u^2+2as
but the answer i am getting is wrong....
is there a different formula you suggest?
 
  • #4
PeterO
Homework Helper
2,426
48
i was trying to use v^2= u^2+2as
but the answer i am getting is wrong....
is there a different formula you suggest?
That is certainly the one I would use.

Were you converting everything to metres and seconds?

This formula will only calculate the acceleration of course - you need at least one more step to get the force.
 
  • #5
16
0
nevermind. i was not converting my answer into kN.... thank you so much!
 

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