# Homework Help: Rolling friction

1. Apr 19, 2007

### pcdagr8

if a rear wheel driven car is accelerated
i think...
1. on rear wheels friction is forward
2 on front wheels it is backward

my questions-
1.wats d direction of rolling friction on the car as a whole?(is dis question correct?)

2.which wheel will have greater magnitude of friction??

2. Apr 19, 2007

### denverdoc

friction is always in direction opposite that of motion.

3. Apr 20, 2007

### pcdagr8

You mean in pure rolling motion the friction should act backward??:surprised :surprised

4. Apr 20, 2007

### Staff: Mentor

friction opposes slipping between surfaces

A better way to describe friction is to say that it always opposes slipping between surfaces. Consider the rear tires. Without friction, they would just spin, slipping to the rear with respect to the road. Friction with the road opposes that slipping by acting towards the front. The friction accelerates the car forward, so friction and the car's motion are in the same direction.

5. Apr 20, 2007

### denverdoc

Thanks Al, a nice explanation. I was only considering situation where there was already angular velocity and see now problem asks during acceleration. My bad.

6. Apr 20, 2007

### pcdagr8

Thanks Al !
but u haven't answered my second question...