# Homework Help: Friction problem of a car

1. Aug 15, 2010

### physicshelp28

In order to stop a car in shortest distance on a horizontal road, how should one apply brakes?

(a) apply the brakes very hard so that wheels stop rotating.
(b) apply the brakes hard enough to just prevent slipping
(c) pump the brakes( press and release)
(d) shut the engine off and not apply brakes.

I know the answer is (b). Please give a solution of it so as to why (b) is the answer.

Its an objective problem of HC Verma Concepts of Physics.

2. Aug 15, 2010

### Staff: Mentor

Why don't you give it a try and explain it to us?

3. Aug 15, 2010

### physicshelp28

I want to but am not able to. m not understanding the concept it seems. Please let me know of this.

4. Aug 15, 2010

### Fallinleave

the reason for choosing B is that to stop the car in a shortest distance, we generally use static friction instead of kinetic friction. The static friction is produced when we are not allow the tires slipping through the road, in this way, the car experiences the maximum friction. For kinetic friction, the tires sliding across the road would produce less friction to stop the car. To review why static friction is bigger than kinetic friction, please read through textbook.

Thanks,