A 1400 kg car with 220 kg of passengers and cargo is moving at 48 m/s. Suddenly, the driver applies the brakes and the car skids to a stop. What happens to the momentum that the car (and its contents) had before braking?
According to the principle of conservation of momentum, the total momentum of a closed system remains constant if no external forces act on it. In this case, the car and its contents make up a closed system.
Before braking, the car and its contents have a certain momentum due to their mass and velocity. This momentum can be calculated as the product of the total mass and the velocity:
Momentum before braking = (total mass) x (velocity)
= (1400 kg + 220 kg) x (48 m/s)
= 67,200 kg·m/s
When the driver applies the brakes, an external force is acting on the car, causing it to decelerate and come to a stop. As the car slows down, its momentum decreases. Eventually, when the car comes to a stop, its momentum becomes zero.
Therefore, the momentum that the car (and its contents) had before braking decreases and eventually becomes zero when the car stops.