Question

train 120m long is running at a speed of 50 Km/hr. What time will it take to cross a 130m

long bridge?​

Answer 1

Answer:

Given :-

A train of length 120 meters long is running at a speed of 50 km/hr .

Length of bridge = 130 long

Required to find :-

Time taken to cross the bridge

Formula used :-

\huge{\dagger{\boxed{\rm{ Time = \dfrac{ Distance }{ Speed }}}}}†

Time=

Speed

Distance

Units Conversion :-

In order to solve this question we need to convert the units of one physical quantity from one unit to another

The physical quantity whose units needed is " Distance "

Here convert the distance from meters to kilometres .

To convert it just divide it by 1000

So,

we know that

\tt{ 1 \; meter = \dfrac{1}{1000} \; kilometers}1meter=

1000

1

kilometers

Similarly,

120 meters = ? kilometres

\Rightarrow{\tt{ \dfrac{120}{1000} = 0.12 \; kilometers }}⇒

1000

120

=0.12kilometers

130 meters = ? kilometres

\Rightarrow{\tt{ \dfrac{130}{1000} = 0.13 \; kilometres }}⇒

1000

130

=0.13kilometres

Thus , units Conversion is done .

Solution :-

Given that :-

A train of length 0.12 km long is running at a speed of 50 km/hr .

Length of bridge = 0.13 km long

From the above we can conclude that

Length of the train = 0.12 km

Length of the bridge = 0.13 km

Total distance needed to be covered = 0.12 + 0.13

=> 0.25 kilometres

Similarly,

It is also mentioned that ,

Speed of the train is 50 km/hr

We need to find the time taken by the train to cross the bridge .

Here ,we have to use the familiar formula

That is ,

\huge{\dagger{\boxed{\rm{ Time = \dfrac{ Distance }{ Speed }}}}}†

Time=

Speed

Distance

Here, substitute the required values

So, we get

\longrightarrow{\tt{ Time = \dfrac{0.25 }{50 }}}⟶Time=

50

0.25

\longrightarrow{\tt{ Time = \dfrac{ 25 }{5000 }}}⟶Time=

5000

25

\longrightarrow{\tt{ Time = 0.005 \; hours }}⟶Time=0.005hours

Here let's convert this hours into seconds for the factor of simplicity .

Hence,

Multiply it with 3600

This is because

Since ,

1 hours = 60 minutes

But

1 minute = 60 seconds

60 minutes = 60 x 60

=> 3,600 seconds

So,

Time = 0.005 x 3600

Time = 18 seconds