Question

If the car is moving on the level road at a speed of 50 km/h has a wheelbase 4 m, a distance of C.G. from ground 800 mm and distance from rear wheels is 1.2 m. Coefficient of friction is 0.8. What is the retardation if the brakes are applied to all wheels?

(a) 7.8 m/s^2

(b) 6.8 m/s^2

(c) 5.8 m/s^2

(d) 4.8 m/s^2

This question was posed to me during an interview for a job.

Question is from Braking System topic in chapter Braking System of Automobile Engineering

Answer 1

Correct answer is (a) 7.8 m/s^2

The best I can explain: When the brakes are applied on all wheels and the vehicle is moving on the level road, a = μ*g  where ‘μ’ is the coefficient of friction, ‘L’ is wheelbase, ‘x’ is a distance of C.G. from rear wheels, and ‘h’ is the distance of the C.G. from the surface of the road. Therefore a = 0.8 * 9.81 = 7.8 m/s^2.