Question

7. A train 200 m long is running at a 1 pc
speed of 90 km/hr. How much time
will it take to cross a telegraph
post?​

Answer 1

$\displaystyle\huge\red{\underline{\underline{Solution}}}$

FORMULA TO BE IMPLEMENTED

When train crosses only object like tree, lamp post, man, telegraph post then in that condition train covers distances equal to its length

GIVEN

• A train 200 m long

• It is running at a speed of 90 km/hr

TO DETERMINE

The time taken to cross a telegraph post

CALCULATION

The speed of the train

$= \sf{90 \: \: km / hr}$

Converting it in metre / sec unit we get

The speed of the train

$\sf{\displaystyle \: = \frac{90 \times 1000}{3600} } \: \: metre / sec$

$\sf{\displaystyle \: = \frac{90 \times 1000}{3600} } \: \: metre / sec$

$\sf{\displaystyle \: = 25} \: \: metre / sec$

Since the train crosses only telegraph post

So in that condition train covers distances equal to its length

So the required time is

$= \displaystyle \: \sf {\frac{ Distance \: Covered \: \: }{Speed \: of \: the \: train}}$

$= \displaystyle \: \sf{ \: \frac{200}{25} \: } \: \: seconds$

$= \displaystyle \: \sf{ 8} \: \: seconds$