What are practical examples of momentum change?

Practical examples of momentum change include car crashes, bouncing balls, rocket launches, and billiard games.

In a car crash, the momentum of the car changes drastically. Before the crash, the car has a certain momentum based on its mass and velocity. When it hits another car or a stationary object, its velocity changes abruptly, which results in a change in momentum. This is why seatbelts are so important - they help to slow down the change in momentum by extending the time it takes for the body to stop moving, reducing the force experienced by the passengers.

Bouncing balls also demonstrate momentum change. When a ball is dropped, it gains momentum as it falls due to gravity. When it hits the ground, its direction of motion changes - it moves upwards. This change in direction means that the velocity of the ball has changed, and hence its momentum has changed. The ball continues to lose momentum as it rises until it stops and falls again, repeating the cycle.

Rocket launches are another great example. A rocket on the launch pad has zero momentum. When the engines are fired, the rocket gains momentum as it accelerates upwards. The momentum of the rocket continues to increase as long as the engines are providing thrust. The momentum of the rocket is transferred to the exhaust gases, which are expelled downwards with equal and opposite momentum.

In a game of billiards, when a player strikes a ball, it moves with a certain momentum depending on the force and direction of the strike. When this ball hits another ball, its momentum is transferred to the second ball, causing it to move. If the first ball comes to a stop after the collision, it means all its momentum has been transferred to the second ball. This is a clear demonstration of the conservation of momentum.