Calculating Force: Rifle & Wood Bullet Impact

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Homework Help Overview

The problem involves a rifle firing a bullet that penetrates a block of wood, with the goal of calculating the resistive force exerted by the wood on the bullet. The context includes parameters such as the bullet's mass, speed, and penetration depth.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the time it takes for the bullet to come to rest and question the calculations related to acceleration and force. There is an exploration of using kinematic equations, particularly SUVAT, to analyze the bullet's motion.

Discussion Status

The discussion is ongoing, with participants offering different perspectives on the calculations and questioning the assumptions made regarding the resistive force and its implications on the bullet's deceleration.

Contextual Notes

There appears to be confusion regarding the application of formulas and the interpretation of the results, particularly in relation to the force calculated and the time taken for the bullet to stop.

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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