A car that weighs 1.30×10^{4} N is initially moving at 40 km/h when the brakes are applied and the car is brought to a stop in 15 m. Assuming the force that stops the car is constant, find

a) the magnitude of that force and

b) the time required for the change in speed. If the initial speed is doubled, and the car experiences the same force during the braking, by what factors are

c) the stopping distance and

d) the stopping time multiplied?

(There could be a lesson here about the danger of driving at high speeds.)