A freight train 420 m long at a speed of 10 m / s and an electric train 120 m long at a speed of 30 m / s

A freight train 420 m long at a speed of 10 m / s and an electric train 120 m long at a speed of 30 m / s follow parallel railway tracks in one direction. how long will the electric train overtake the freight train? the movement of trains is considered uniform.

Given:

L1 = 420 meters – the length of the freight train;

v1 = 10 meters per second – the speed of the freight train;

L2 = 120 meters – length of the electric train;

v2 = 30 meters per second – the speed of the electric train.

It is required to determine t (second) – the time during which the electric train will overtake the freight train.

According to the condition of the problem, an electric train and a freight train are moving in the same direction. Then, the total length of trains is equal to:

L = L1 + L2 = 420 + 120 = 540 meters.

The speed of the electric train relative to the freight train is:

v = v2 – v1 = 30 – 10 = 20 meters per second.

The overtaking time will be equal to:

t = L / v = 540/20 = 27 seconds.

Answer: an electric train will overtake a freight train within 27 seconds.