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 the front wheels?

(a) 3.4 m/s^2

(b) 2.4 m/s^2

(c) 1.4 m/s^2

(d) 4.4 m/s^2

I have been asked this question in unit test.

The question is from Braking System topic in portion Braking System of Automobile Engineering

Answer 1

Correct option is (b) 2.4 m/s^2

The best explanation: When the brakes are applied on the front wheels and the vehicle is moving on the level road, a = \(\frac{\mu * g * x}{L-\mu* h}\)  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 = \(\frac{0.7 * 9.81 * 1.2}{4-(0.8 * 0.8)}\) = 2.4 m/s^2.