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October 27, 2017 STUDENT NAME 1 STOPPING DISTANCE (20 POINTs) A car of mass m 17

ID: 1790177 • Letter: O

Question

October 27, 2017 STUDENT NAME 1 STOPPING DISTANCE (20 POINTs) A car of mass m 1700 kg is traveling at 75 mph when the driver slams the brakes and (a) Ignoring the reaction time of the driver and friction, find the stopping distance skids to a halt. if the car is traveling up a 10° straight slope. (b) Ignoring the reaction time of the driver, and assuming that the coefficient of kinetic friction between the tires of the car and the road is k-0.8, find the stopping distance if the car is traveling on a straight level road.

Explanation / Answer

Mass = m = 1700 kg

Speed = v = 75 mph = 33.5 m/s

b) Kf = 0

     fk = µk*F = µk*mg

    W = Kf – Ki = -0.5*m*vo^2

    W = fk*x = µk*mg*x

   µk*mg*x = -0.5*m*vo^2

   | x | = 0.5*vo^2/( µk*g) = 33.5^2/(2*0.8*9.8) = 71.6 m