Calculating Force: Rifle & Wood Bullet Impact

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SUMMARY

The discussion focuses on calculating the resistive force exerted by wood on a bullet fired from a rifle. The bullet, weighing 7.06 grams and traveling at a speed of 449 m/s, penetrates 12.9 cm into the wood, resulting in a calculated resistive force of 5516.6785 N. Participants clarify the method for determining the time it takes for the bullet to come to rest using the formula t = v/a, where 'a' is derived from the force and mass of the bullet. The conversation emphasizes the importance of correctly applying the equations of motion in physics.

PREREQUISITES
  • Understanding of Newton's Second Law (F = ma)
  • Familiarity with kinematic equations (SUVAT)
  • Basic knowledge of force and motion concepts
  • Ability to perform unit conversions (grams to kilograms)
NEXT STEPS
  • Study the derivation and application of Newton's Second Law in various contexts
  • Learn about kinematic equations and their applications in projectile motion
  • Explore the concept of resistive forces in different materials
  • Investigate the effects of bullet penetration in various media
USEFUL FOR

Physics students, educators, and anyone interested in understanding the dynamics of projectile motion and impact forces.

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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