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Physics Properties Of Matter Level: High School

Pascal’s Law

Depressing the brake pedal in a car pushes on a piston with cross-sectional area 2.0 cm^2 . The piston applies pressure to the brake fluid , which is connected to two pistons , each with area 12.3 cm^2 . Each of these pistons presses a brake pad against one side of a rotor attached to one of the rotating wheels . See the figure at “click here” .

a) When the force applied by the brake pedal to the small piston is 7.8 N , what is the normal force applied to each side of the rotor ?

b) If the coefficient of kinetic friction between a brake pad and the rotor is 0.80 and each pad is (on average) 11 cm from the rotation axis of the rotor , what is the torque on the rotor due to the two pads ?