Question

** muuta
A 75 m long train crosses a bridge of length
300 m'in 15 seconds. What is the speed of the train
in km/h?​

Answer 1

Answer :

Speed of the train = 90 km/hr.

___________

Given:-

• Length of train is 75 m
• Length of the bridge is 300 m
• Time taken by train to cross the bridge is 15 sec.

Find:-

Speed of the train in km/hr.

Solution:-

$\boxed{\bold{\sf{Speed\:=\:\dfrac{Distance}{Time}}}}$ ....(1)

Now,

Distance covered by train to cross the bridge = Length of train + Length of bridge

$\implies$ 75 + 300

$\implies$ 375 m

Given time is 15 sec.

Substitute the known values in the known formula

$\implies$ $\sf{Speed\:=\:\dfrac{375}{15}}$

$\implies$ Speed = 25 m/s

But according to question, we have to find the speed of the train in km/hr.

So,

To convert m/s into km/hr. multiply it by 18/5.

$\implies$ $\sf{Speed\:=\:25\:\times\:\dfrac{18}{5}}$

$\implies$ Speed = 25 × 3.6

$\implies$ Speed = 90 km/hr.

OR

$\implies$ Distance covered by train = 375 m

$\implies$ $\sf{\dfrac{375}{1000}}$

$\implies$ 0.375 km

Also,

Time taken by train to cross the bridge is 15 sec.

$\implies$ $\sf{\dfrac{15}{3600}}$

$\implies$ 0.00417 hrs.

Substitute the known values in above formula

$\implies$ $\sf{Speed\:=\:\dfrac{0.375}{0.00417}}$

$\implies$ Speed = 89.9 km/hr.

$\implies$ Speed = 90 km/hr. (approx.)

•°• Speed of the train is 90 km/hr.

Answer 2

Question :----- what is the speed of Train in km/h ..

Given :---------

• Length of Train = 75m
• length of birdge = 300m
• Time to cross = 15 second .

Solution :--------

Formula to be used :-----

• Speed = Distance/Time
• m/s to km/h = 18/5

Total distance train will cover while crossing the bridge = length of train + length of bridge ...

so, Total distance will be = 300+75 = 375 m

Now it is given that Train takes 15 seconds to cross the bridge ..

That means train takes 15 seconds to cover 375 m distance ...

so,

speed of Train = D/T = 375/15 = 25 m/s

speed of Train = 25×(18/5) = 90km/h .....

So, speed of Train is 90km/h .....

[ To change km/h speed in m/s we multiply it by 5/18 ]