Question

If the car is moving on the level road at a speed of 50 km/h has a wheelbase 3 m, a distance of C.G. from ground 700 mm and distance from rear wheels is 1.1 m. Coefficient of friction is 0.7. What is the retardation if the brakes are applied to the rear wheels?

(a) 3.7 m/s^2

(b) 2.7 m/s^2

(c) 1.7 m/s^2

(d) 4.7 m/s^2

The question was asked during an online exam.

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

Answer 1

The correct answer is (a) 3.7 m/s^2

Best explanation: When the brakes are applied on the rear wheels and the vehicle is moving on the level road, a = \(\frac{\mu * g * (L-x)}{L+μ * h}\) 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 = \(\frac{0.7 * 9.81 * (3-1.1)}{3+(0.7 * 0.7)}\) = 3.7 m/s^2.