How Much Force Accelerates a Bullet in a Rifle?

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SUMMARY

The discussion focuses on calculating the force required to accelerate a bullet in a rifle, specifically one that exits the muzzle at 800 m/s from a barrel length of 80 cm and a bullet mass of 20 g. The correct approach involves using the formula F = ma, where the acceleration is derived from the change in velocity over time, resulting in an acceleration of 8000 m/s². The final force calculated is 8000 N, which aligns with the provided answer, emphasizing the importance of understanding the physics rather than just obtaining the answer.

PREREQUISITES
  • Understanding of Newton's Second Law (F = ma)
  • Basic knowledge of kinematics and acceleration
  • Familiarity with unit conversions (grams to kilograms, centimeters to meters)
  • Ability to manipulate algebraic equations
NEXT STEPS
  • Study kinematic equations for uniformly accelerated motion
  • Learn about the implications of constant vs. variable acceleration
  • Explore the relationship between force, mass, and acceleration in different contexts
  • Review unit conversion techniques for physics calculations
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This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of projectile motion and the forces involved in firearm mechanics.

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Homework Statement



A rifle bullet leaves the muzzle of a gun at 800. m/sec. The rifle barrel is 80. cm long and the mass of the bullet is 20.g. What force was needed to accelerate the bullet?

Homework Equations



Formulas:

F(Total)= ma

F= mg

F = micrometers (m)(g)

The Attempt at a Solution



t= 80 \div 800 = .1s

a= 800 - 0 \div .1 = 8000 m/s^2

The answer is provided on my sheet as 8000 N, but I don't have a clue as to how to do that. Its the closest I've gotten to the answer.
 
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Welcome to PF;
The equation you used was for time assumed a constant speed along the barrel - but if the bullet travels at a constant speed, then the force must be zero.

if you imagine the bullet has constant acceleration from rest to 800m/s along the length of the barrel, then you use a kinematic equation to find the acceleration.

note: it is best practice to complete the algebra before using the numbers.
 
Thanks for the help. Did you get the answer "8000 N" just like I did this time around?
 
I do not, as a rule, actually complete the problems here.
That's your job ;)

You'll find that the answer is not as important as your understanding of the physics behind it.
 

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