When a car moves on a road, then the bottommost point is always at rest relative to the ground at that particular instant and since friction only opposes relative motion between two bodies then according to this there should be no friction acting on the bottommost point of the wheel. If this is the case then according to Newton's 1st law, the car should continue to move forever unless brakes are applied. But in reality this doesn't happen & as the accelerator is released the car moves for sometime & ultimately stops even though no brakes are applied. How is this possible?
When a car moves on a road, then the bottommost point is always at rest relative to the ground at that particular instant and since friction only opposes relative motion between two bodies then according to this there should be no friction acting on the bottommost point of the wheel. If this is the case then according to Newton's 1st law, the car should continue to move forever unless brakes are applied. But in reality this doesn't happen & as the accelerator is released the car moves for sometime & ultimately stops even though no brakes are applied. How is this possible?
It is because the patch of rubber that is actually touching the road is not moving with respect to the road. It is static (for a very brief period every revolution).
As the patch flattens out on the road, there is a tiny bit of relative motion, which is part of that rolling friction, but the whole patch is not sliding, so it’s not kinetic friction (unless you have slammed on the brakes and the wheels are screeching or you are cornering so hard the tires are slipping).
So this rolling friction is responsible for the stopping of car after some time even without applying the brakes
It is because the patch of rubber that is actually touching the road is not moving with respect to the road. It is static (for a very brief period every revolution).
As the patch flattens out on the road, there is a tiny bit of relative motion, which is part of that rolling friction, but the whole patch is not sliding, so it’s not kinetic friction (unless you have slammed on the brakes and the wheels are screeching or you are cornering so hard the tires are slipping).
So this rolling friction is responsible for the stopping of car after some time even without applying the brakes
