Question

Two cars A and B are approaching each other on straight road with speed 72 km/h and 90 km/h respectively. They spot each other when they are 500 m apart. If their reaction time is 0.5 s. Find the distance between them if they apply breaks producing same retardation of 5 m/s.
(1) 397.5 m
(2) 102.5 m
(3) 375 m
(4) 125 m​

Answer 1

Answer:

375 m

Explanation:

Two cars A and B are approaching each other on straight road with speed 72 km/h and 90 km/h respectively. They spot each other when they are 500 m apart. If their reaction time is 0.5 s. Find the distance between them if they apply breaks producing same retardation of 5 m/s

Speed of car A = 72 km/hr = 72 * 5/18  = 20 m/s

Speed of Car B = 90 km/hr = 90 * 5/18 = 25 m/s

Distance between them = 500 m

Distance covered in 0.5 sec = 20 * 0.5 + 25 * 0.5 = 22.5 m

retardation of 5 m/s.

V² - U² = 2(-a)S  here final velocity = 0  S = U²/2a

Distance by Car A = 20²/2*5  = 40 m

Distnace by Car B = 25²/2*5 = 62.5 m

Total distance traveled  = 22.5 + 40 + 62.5 = 125

Distance between Cars = 500 - 125 = 375 m