Question

.A train of length 120 m, travelling at 30 m/s takes
30 s to overtake another train of length 240 m. If
both the trains are travelling in the same direction,
then find the speed of the longer train.​

Answer 1

Answer:

Relative motion

Total distance train has to travel

= 120 + 240 = 360 m

Let velocity of other train is v , relative velocity will be v - 30 because trains are going in same direction .

So time

$t = \frac{360}{v - 30} = 30 \\ \\ 360 = 30v - 90 \\ \\ 30v = 450 \\ \\ v = 15 \: \: \frac{m}{s}$

Answer 2

$Relative motion</p><p></p><p>Total distance train has to travel</p><p></p><p>= 120 + 240 = 360 m</p><p></p><p>Let velocity of other train is v , relative velocity will be v - 30 because trains are going in same direction .</p><p></p><p>So time</p><p></p><p>\begin{lgathered}t = \frac{360}{v - 30} = 30 \\ \\ 360 = 30v - 90 \\ \\ 30v = 450 \\ \\ v = 15 \: \: \frac{m}{s}\end{lgathered}t=v−30360=30360=30v−9030v=450v=15sm</p><p></p><p>$