Question

A driver applies the brakes and reduces the speed of her car by 20%, without changing the direction in which the car is moving. By how much does the car’s momentum change?

a) 80%
b) 20%
c) 0%
d) 10%

Answer 1

The car's momentum changes by 20%. The correct answer is b) 20%.

Step-by-step explanation:

The momentum of an object is given by the product of its mass and velocity. In this case, the driver reduces the speed of the car by 20%.

This means that the final speed of the car is 80% of the initial speed. As momentum is directly proportional to velocity, reducing the speed by 20% also reduces the momentum by 20%, making the correct answer (b) 20%.

When a driver applies the brakes and reduces the speed of her car by 20% without changing the direction in which the car is moving, the car's momentum changes by the same percentage as the speed, which is 20%. This is because momentum, given by the product of mass and velocity (p = mv), is directly proportional to the velocity when the mass of the car remains constant.