# A train previously at rest starts accelerating. It takes 4 seconds for the first carriage to cross the reference point K. How long will it take for the 10th carriage to cross the same point? (All carriages are the same width)

##### 2 Answers

#### Explanation:

Let the length of each carriage be

Suppose that train accelerates at a constant rate of acceleration

We use the kinematic equation

where

Inserting various values for the first carriage we get

From (1)

Time taken to pass

Similarly time taken to pass

Therefore time taken by tenth carriage to pass through the reference point

#### Explanation:

α=

u is the speed gained in 4 secs

L=

L is the length of a carriage

t=

Δt