Question

Consider a car moving along a straight horizontal road with a speed of 72km/h. If the coefficient of static friction between the tyres and the road is 0.5, the shortest distance in which the car can be stopped is? (g=10m/s^2)

(a) 30m

(b) 40m

(c) 72m

(d) 20m

Answer 1

Correct option is (b) 40m

For explanation I would say: Retardation, a = -μg = -0.5×10 = -5m/s^2

u = 72km/h = 20m/s

As v^2-u^2=2as

s = 40m.