Question

train 75m long moving at a speed of 54 kmh–1, starts overtaking another train of length 125m moving at a speed of 36 kmh–1 on a parallel track. how long will the first train take to completely overtake the second train?​

Answer 1

It takes 40 s to cross second train completely

Given

A train 75 m long moving at a speed of 54 km/h , starts overtaking another train of length 125 m moving at a speed of 36 km/h on a parallel track

To Find

Time taken to cross second train completely

Concept Used

$\bf \pink{\bigstar\ \; Speed=\dfrac{Distance}{Time}}\\\\\bf \green{\bigstar\ \; S=\dfrac{D}{t}}$

Solution

Length of train-1 = 75 m

Speed of train-1 = 54 km/h = 15 m/s

Length of train-2 = 125 m

Speed of train-2 = 36 km/h = 10 m/s

So ,

Distance , D = Length of train-1 + Length of train-2

⇒ D = 65 + 125

⇒ D = 190 m

Relative speed , S = Speed of train-1 - Speed of train-2

⇒ S = 15 - 10

⇒ S = 5 m/s

Apply formula ,

$\bf \red{\bigstar\ \; S=\dfrac{D}{t}}\\\\\to \rm 5=\dfrac{200}{t}\\\\\to \rm t=\dfrac{200}{5}\\\\\to \bf \blue{t=40\ s\ \; \bigstar}$

So , It takes 40 s to cross second train completely

Answer 2

Given :-

• A train 75m long is moving at a speed of 54 kmh-¹ starts overtaking another train of length 125m moving at a speed of 36 kmh-¹ on a parallel track.

To Find :-

• Time required by the first train to overtake second train.

Solution :-

Speed Of First Train = 54km/h = 15m/s.

Length Of First Train = 75m.

Speed Of Second Train = 36km/h = 10m/s.

Length Of Second Train = 125m.

Now, Total Distance :-

➨ 125 + 75 = 200m.

Now, Relative Speed :-

➨ 15 - 10 = 5m/s.

We know that,

Speed = Distance/Time.

➨ 5 = 200/Time.

➨ Time = 200/5.

➨ Time = 40.

Hence, Time required by the first train to overtake second train = 40 seconds.