# Physics rifle problem -- Forces and acceleration of the bullet

• chemie726283
In summary, a rifle bullet with a mass of 10g takes 2.0 ms to travel down a 0.50m long barrel with constant acceleration. The muzzle velocity of the bullet can be calculated using the suvat equations. The acceleration in the barrel can also be calculated using the suvat equations. After hitting a target and penetrating 2.5 cm, the average force acting on the bullet while it comes to rest can be found using F = ma.
chemie726283

## Homework Statement

A rifle bullet of mass 10g is fired and takes 2.0 ms to travel down the rifle barrel of length 0.50m with constant acceleration

1. Calculate the muzzle velocity (bullet velocity on leaving the barrel)
2. Calculate the acceleration in the barrel
3. After traveling a short distance through air, the resistance of which can be neglected, the bullet hits a target and penetrated to a depth of 2.5 cm. Calculate the average force acting on of the bullet while it is coming to rest.

## The Attempt at a Solution

m=10 t=2ms=0.002 s l=0.5 m
1. I don't know this one but I need it to get the other answers
2. a = 0-v/0.002 Then use v that I get in 1)?
3. Do I just use F = ma here? after getting a in 2)

Last edited by a moderator:
I suggest you look up and study the suvat equations. They are basic kinematic relations for motion with constant acceleration.

## 1. What is the formula for calculating the acceleration of a bullet?

The formula for calculating the acceleration of a bullet is a = (Fnet)/m, where a is the acceleration, Fnet is the net force acting on the bullet, and m is the mass of the bullet.

## 2. How does the force of gravity affect the trajectory of a bullet?

The force of gravity has a significant impact on the trajectory of a bullet. As the bullet travels through the air, it is constantly being pulled downward by the force of gravity. This causes the bullet to follow a curved path, known as a parabola.

## 3. Can you explain the difference between muzzle velocity and muzzle energy?

Muzzle velocity refers to the speed at which the bullet leaves the barrel of the rifle. Muzzle energy, on the other hand, is a measure of the bullet's kinetic energy at the instant it leaves the muzzle. Muzzle energy takes into account both the speed and mass of the bullet, while muzzle velocity only considers the speed.

## 4. How do external factors, such as air resistance, affect the acceleration of a bullet?

Air resistance, also known as drag, acts in the opposite direction of the bullet's motion and can significantly reduce its acceleration. As the bullet travels through the air, it collides with air molecules, causing a force that opposes its motion. This force increases as the bullet's speed increases and can ultimately limit its acceleration.

## 5. How does the force applied by the rifle's firing mechanism affect the acceleration of the bullet?

The force applied by the rifle's firing mechanism, also known as the firing pin, produces an initial acceleration of the bullet. This force is crucial in overcoming the inertia of the bullet and propelling it forward. However, the acceleration of the bullet will continue to be affected by other forces, such as air resistance and gravity, once it leaves the barrel of the rifle.

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