Question

The car is moving up on the 12o 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 0.7. What is the retardation of the car if the brakes are applied to all the four wheels?

(a) 8.75 m/s^2

(b) 8.81 m/s^2

(c) 7.71 m/s^2

(d) 6.81 m/s^2

This question was posed to me in an international level competition.

I would like to ask this question from Braking System topic in section Braking System of Automobile Engineering

Answer 1

Right choice is (a) 8.75 m/s^2

Easy explanation: α is the inclination angle in degree = 12°, μ is the coefficient of friction = 0.7. When the vehicle is moving up on the inclined road and brakes are applied to all four wheels than the retardation a = g*(μ*cosα + sinα) = 9.81*(0.7*cos12° + sin12°) = 8.75 m/s^2.