A daredevil driver knows that the coefficient of kinetic friction between his ti
ID: 2052833 • Letter: A
Question
A daredevil driver knows that the coefficient of kinetic friction between his tires and the road is k=0.40. He and his car (total mass 2000 kg) zoom downhill on a 15o incline toward a brick wall at an initial speed of 53.6 m/s and slams on the brakes so as to come to rest just before hitting the wall.
a.) What is the net force on the daredevil’s car? (Not just an aswer, solution please)
b.) How far before the wall should he slam on the brakes if he wants to give himself a
2 m margin of error? (A formula would be sufficient)
Explanation / Answer
Weight component along the incline = mg sin15 = 5072.8 N Normal reaction = mg cos 15 = 18932 N Friction = uN = 0.4*18932 = 7572.8 N (a)Net force = 7572.8 - 5072.8 = 2500 N (b) Acceleration = 2500/2000 = 1.25 m/s^2 So, distance = v^2 - u^2/2a +2 = 53.6^2/2*1.25 +2 = 1151.184 m