Rifle Recoil

Classical Mechanics Level 2

Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. Which of the following statements is true concerning the acceleration of the recoiling rifle?

It is smaller than the acceleration of the bullet. It is equal in magnitude with the acceleration of the bullet. It is greater than the acceleration of the bullet. None of the above.

2 solutions

Abishek Nathan
Dec 20, 2014

By Newton's second law of motion, F=m×a. Since the mass of the gun is greater than the bullet, gun has small acceleration.

We can also say that as conservation of momentum..

Sanjay R - 3 months, 1 week ago

Aditya Raj
Dec 17, 2014

The force on the rifle equals the force on the bullet. Yet, acceleration depends on both force and mass. The bullet has a greater acceleration due to the fact that it has a smaller mass. Remember: acceleration and mass are inversely proportional.

Theoretically, the mass of bullet could be greater then the mass of rifle, so "None of the above" is right...

Jan Pajout - 4 years, 10 months ago

A rifle whit a higher recoil than the acceleration imparted to the bullet it fires would be extremely dangerous. And if you are thinking of something like a cannon , attached to the ground, that fires a bullet which has a mass greater than its own, than you should take into account all of the fixed mass it is attached to (presumably a big portion of Earth's total mass), and you would be back to the correct answer about the recoil:

$\boxed{\text{It is smaller than the acceleration of the bullet.}}$

Michele Polli - 1 year, 10 months ago

Rifle Recoil

2 solutions

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