Calculating Force: Rifle & Wood Bullet Impact

AI Thread Summary
A rifle fires a 7.06 g bullet at a speed of 449 m/s, which penetrates a block of wood to a depth of 12.9 cm, resulting in a calculated resistive force of 5516.6785 N. The discussion centers on determining the time it takes for the bullet to come to rest, with an initial attempt using the formula t = v/a yielding an incorrect result. Participants suggest calculating the bullet's deceleration and applying SUVAT equations for a more accurate solution. The conversation highlights the need to correctly apply physics principles rather than relying solely on force calculations. Ultimately, the focus is on understanding the relationship between force, acceleration, and time in this context.
Jjolly65
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Homework Statement




A rifle with a barrel length of 50.86 cm fires a 7.06 g bullet with a horizontal speed of 449 m/s. The bullet strikes a block of wood and penetrates to a depth of 12.9 cm.


What resistive force (assumed to be constant) does the wood exert on the bullet?
5516.6785 N


The Attempt at a Solution



How long does it take the bullet to come to rest?
Shouldn't it just be t = v/a t = 449/ 5516.6785 = 8.14*10-2
Thats what I'm getting but its saying I am wrong... Am I missing something?
 
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F = ma

Wood exerts 5516.6785 on the bullet like you said, work out the bullets deceleration then try SUVAT
 
You found the force by figuring the acceleration.

t = v/a

That's true. But unfortunately it's not = v / F
 
WoW the rifle is too big. LOL
 

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