# Understand Momentum & Energy Conservation in Ballistic Pendulum Problems

• IKonquer
In summary, a ballistic pendulum is a device used to measure the velocity of a projectile by capturing it in a pendulum and measuring the height to which the pendulum swings after impact. It works by transferring the momentum and energy of the projectile to the entire system, allowing for the calculation of the initial velocity. Momentum and energy conservation are important principles in these problems, but factors such as air resistance and friction can affect the accuracy of the measurement.
IKonquer
In solving a ballistic pendulum problem, you can break it up into two parts:

(1) A bullet is fired and it lodges into a block.
Momentum is conserved because there is no net external force.
Energy is not conserved because there is friction between the block and bullet.

(2) Once the bullet is lodged into the block, the block moves up a certain vertical distance.

Could someone explain:

Why is momentum not conserved in this case?

Why is energy conserved in this case?

Last edited:
Don't you have the parts in bold the wrong way around?

## 1. What is a ballistic pendulum?

A ballistic pendulum is a device used to measure the velocity of a projectile, typically a bullet or a small ball, by capturing it in a pendulum and measuring the height to which the pendulum swings after impact.

## 2. How does a ballistic pendulum work?

When a projectile is fired into the pendulum, it becomes embedded in the pendulum and transfers its momentum and energy to the entire system. This causes the pendulum to swing to a maximum height, which can be measured and used to calculate the initial velocity of the projectile.

## 3. What is momentum conservation in ballistic pendulum problems?

Momentum conservation in ballistic pendulum problems refers to the principle that the total momentum of a closed system before and after a collision remains constant. In other words, the momentum of the projectile before impact is equal to the combined momentum of the pendulum and the projectile after impact.

## 4. How is energy conserved in ballistic pendulum problems?

In a perfect system, energy is conserved in ballistic pendulum problems. This means that the total energy of the system before and after the collision remains constant. The kinetic energy of the projectile before impact is converted into potential energy of the pendulum at its maximum height, and this energy is equal to the initial kinetic energy of the projectile.

## 5. What factors can affect the accuracy of a ballistic pendulum measurement?

Factors that can affect the accuracy of a ballistic pendulum measurement include air resistance, friction, and the elasticity of the pendulum. These factors can cause energy losses and alter the height of the pendulum swing, leading to a less accurate measurement of the projectile's initial velocity.

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