Question

a car is moving with a speed of 50 kilometre per hour can be stopped by brakes after a distance 6 metre if the same car is moving at a speed of hundred kilometre per hour the minimum stopping distance is​

Answer 1

initial speed of car, u = 50km/h

final speed of car, v = 0

distance covered by car after applying brakes , s = 6m

use formula, v² = u² + 2as

or, 0 = (50km/h)² + 2a(6m)

or, a = -(50km/h)²/2(6m) ......(1)

now, initial speed of particle, u = 100 km/h

final speed of particle , v = 0

we have to find minimum stopping distance, D

use formula, v² = u² + 2aD

or, 0 = (100km/h)² + 2aD

from equation (1),

or, 0 = (100km/h)² + 2{-(50km/h)²/2(6m)}D

or, D = (100km/h)²/{2(500km/h)²/2(6m)}

= 6m × [(100km/h)/(50km/h)]²

= 6m × (2/1)²

= 6m × 4 = 24m

hence, minimum stopping distance is 4m