Question

Consider a car moving on a straight road with a speed of 100 m/s. The distance at which a car can be stopped is : (μ_k = 0.5)

(a) 800 m

(b) 1000 m

(c) 100 m

(d) 400 m

 

Answer 1

b) is the correct option i.e. 1000 

When the car is stopped by friction then its retarding force is

ma = μR

ma = μmg

a= μg

Consider the equation v² = u² -2as (the car is retarding so a is negative)

0 = u² -2as

2as = u²

s = u²/2a

s = u²/2μg

s = (100)²/2 x 0.5 x 10

s = 1000 m