Question

Two cars A and B are approaching each other
head-on with speeds 20 m/s and 10 m/s
respectively. When their separation is X then A and
B start braking at 4 m/s2 and 2m/s2 respectively.
Minimum value of X to avoid collision is
(1) 60 m
$2) 75 m
(3) 80 m
(4) 90 m
​

Answer 1

Answer:

(2) 75 m

Explanation:

minimum separation = sum of stoping distance of two cars

Car- A :

u = 20 m/s

a = - 4 m/sq-sec

s = (v^2 - u^2) / 2a = - 20×20 / (- 2 × 4) = 50 m

stoping distance = 50 m

Car- B :

u = 10 m/s

a = - 2 m/sq-sec

s = - 10×10 / (- 2×2) = 25 m

stoping distance = 25 m

so,

minimum value of -

x = 50 + 25 = 75 m