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Work, Energy, Friction

A car is travelling on a level road with speed v1 at the instant when the brakes are applied. Assume that the wheels are locked and the car is skidding, so the friction force between the tires and the road is kinetic friction with coefficient mu_k.

a) Use the work-energy relation to calculate the minimum stopping distance of the car in terms of v1, mu_k, and the acceleration g due to gravity.

b) It is observed that the car stops in a distance of 120 feet if v1 is 30.00 m/hr. What is the stopping distance if v1= 60 m/hr? Assume that mu_k and hence the kinetic friction force remains the same.