A passenger of a train traveling at a speed of 15 m / s sees through the window an oncoming train 150 m l

A passenger of a train traveling at a speed of 15 m / s sees through the window an oncoming train 150 m long for 6 seconds. What is the speed of the oncoming train?

Let’s find the speed of the first train relative to the second. If a car of length L is visible for a time t, then this speed is

v = L / t;

v = 150/6 = 25 m / s.

Since trains move towards each other with their own speeds v1 and v2, respectively, the relative speed of one relative to the second can be found by the formula

v = v1 + v2,

whence the speed of the second train is

v2 = v – v1;

v2 = 25 – 15 = 10 m / s.