Question

The car is moving down on the 14° inclined road with horizontal at 36 km/h which is having wheelbase 1.4 m. The C.G. of the car is 0.9 m above the road. The coefficient of friction is 0.75. What is the retardation of the car if the brakes are applied to all the four wheels?

(a) 4.76 m/s^2

(b) 5.76 m/s^2

(c) 6.76 m/s^2

(d) 7.76 m/s^2

I got this question in unit test.

My question is based upon Braking System in chapter Braking System of Automobile Engineering

Answer 1

The correct answer is (a) 4.76 m/s^2

To explain I would say: α is the inclination angle in degree = 14° μ is the coefficient of friction = 0.75. When the vehicle is moving down on the inclined road and brakes are applied to all four wheels than the retardation a = g*(μ*cosα – sinα) = 9.81*(0.75*cos14° – sin14°) = 4.76 m/s^2.