How is ABS related to static and kinetic friction?

Like, how are static and kinetic friction involved in the Anti-lock Braking System?


Thanks.|||When a vehicle moves the wheels roll freely and the friction between the wheel and the road surface is of the higher static type. When the brake is applied heavily the wheel tends to lock causing the friction to change to the lower kinetic type. The Anti-lock Braking System acts to momentarily release the applied brake at that instant just before wheel lock to keep the static friction. When that wheel rolls freely the brake is applied again and the process keeps on producing in effect the maximum braking.|||Just so you know, neither regime of friction has anything to do with electrostatics. Do not let the naming of "Coulomb friction" and "Coulomb's law" deceive you, they have nothing to do with each other.





Think of static friction as traction. It is the constraint force that prevents (until it is demanded more than mu_s*N) relative sliding motion.





Think of kinetic friction as skidding...it is what slows sliding down to a grinding halt, dissipates heat, and wears out materials. Kinetic friction occurs once relative sliding is already the case, and it just tries to bring the relative sliding to a halt.








When you are slowing down a car, you want no skidding of tires on asphalt, and you want static friction to be the force from the road on the car.





If your wheels lock up, your car will skid freely, and you cannot steer, but you just skid to a grinding halt in the direction you were traveling at time of wheel locking.





Locking of the wheels by the brakes occurs when the shoes clamp the drum so much that the wheels come to a grinding halt relative to the car before the entire car slows down. If you demand too much from the brakes, the wheels lock and you cannot stop or steer your car as well.





For this reason, antilock braking systems (ABS) are designed to ease the shoe-on-drum pressure such that they pump the brakes and avoid the wheel-locking. Manual abs involved drivers to be properly trained to apply pumping foot action, but modern automatic ABS does it for the driver.





Bottom line: keep the kinetic friction between brake shoe and brake drum, and keep static friction between the tire and road.|||when ceramic brake pads compress against the vehicles rotor, friction is applied to the rotor that is in motion (kinetic)





static arises from this as well (think of when you rub socks on carpet)