Question

A 2000-kg car is traveling at 20 m/s on a horizontal road and the engine suddenly is broken down. The brakes immediately are applied and the car skids to a stop in 4.0 s with a constant acceleration because of kinetic friction. What is the coefficient of kinetic friction between the tires and road?

Answer 1

Here given the mass of the car,

The velocity of the car before applying break,

When the car breaks down,the dirver sudden applies break leads to the skidding of the vehicle along the road.

So,from the free body diagram of the car in this condition as shown,

Here the car is comes to rest by the frictional force between the road and tyres of the car.

We have the normal force on the car by road,

So,the frictional force on car by road,N

So,The acceleration of the car(retardation),m/s^2

Also given the time in which the car stops,

Alsothe final veloctiy of car,

From the Newton's 1st equation of motion,

ie,

So,Coefficcient of kinetic friction,

So,The coefficcient of kinetic friction between roads and tyres,