Question

a train is traveling at a speed of 90 km hr-^1. brakes are applies so as to produce uniform acceleration of -5.0ms-^2. find how far will the train go before coming at rest

Answer 1

ANSWER :

Given :

▪ Initial speed of train = 90kmph

▪ Retardation of train = 5m/s^2

To Find :

▪ Distance covered by train before coming at rest.

Concept used :

๏ This question is completely based on concept of stopping distance.

Formula Derivation :

✒ v^2 - u^2 = 2as

✒ (0)^2 - u^2 = 2(-a)s

✒ -u^2 = -2as

✒ s = u^2/2a

• s denotes stopping distance
• u denotes initial velocity
• a denotes retardation

Conversion :

✳ 1kmph = 5/18mps

✴ 90kmph = 90×5/18 = 25mps

Calculation :

→ s = u^2/2a

→ s = (25)^2/(2×5)

→ s = 625/10

→ s = 62.5m