Question

An automobile traveling at speed can be stopped in distance by applying brakes. The same automobile moving at a certain speed was stopped in distance . It follows that the automobile was travelling at speed :

Answer 1

Initial velocity, u = 40 km/h = 40 × (5/18) = 200/18 m/s

Final velocity, v = 0

Distance travelled before coming to rest, s = 2 m

Using, v2 = u2 + 2as

=> a = -u2/(2s)

=> a = -30.864 m/s2

Again,

u = 80 km/h = 400/18 m/s

v = 0

a = -30.864m/s2

Now, v2 = u2 + 2as

=> s = -u2/(2a) = 8 m