So according to my textbook applying the brakes hardly to essentially lock up the wheels causes skidding which is kinetic friction so the breaking distance is longer. However, if the brakes were "pumped" the card would not skid and it will be considered static friction so the braking distance is shorter. I UNDERSTAND that the coefficient of static friction has a greater magnitude than kinetic friction, so it makes sense as to why static has a greater deceleration and shorter brake distance. HOWEVER, I do not understand why skidding is considered kinetic friction and not static friction; and why "pumping" the brakes causes static friction. Can someone please explain to how they are so?
[Physics] Why is skidding considered kinetic friction when braking on a car
frictionstatics
Best Answer
Kinetic friction is all about trying to stop one surface from skidding against another surface. When you have two things such as the wheel and the ground sliding against each other, this is kinetic friction. However, when the wheels are rotating, there is static friction between the ground and the wheel. This is because the wheel is rolling and not sliding against the ground. A point on the wheel only contacts the ground for a very very small instant per revolution, so this is static because there isn't sliding between the ground and the wheel.