Question

Два поезда движутся навстречу друг другу со скоростями 72 и 54 км,ч. Пассажир ,находящийся в первом поезде,замечает, что второй поезд проходит мимо него в течении 14 сек. Какова длинна второго поезда???

Answer 1

Относительно пассажира (так как он сам движется в 1-м поезде навстречу 2-му поезду) второй поезд движется со скоростью v=72+54=126 (км/час) =126000 м/час=35 м/сек. Поэтому длина 2-го поезда L=14•35=490 (м).

Answer 2

Problem Analysis

We have two trains moving towards each other with speeds of 72 km/h and 54 km/h. A passenger in the first train notices that the second train passes by in 14 seconds. We need to find the length of the second train.

Solution

To find the length of the second train, we can use the formula:

Length of the second train = Relative speed × Time taken to pass

The relative speed of the two trains is the sum of their speeds, as they are moving towards each other. So, the relative speed is 72 km/h + 54 km/h = 126 km/h.

Now, we need to convert the relative speed from km/h to m/s, as the time is given in seconds. We know that 1 km/h is equal to 0.2778 m/s.

Relative speed = 126 km/h × 0.2778 m/s = 35 m/s

Substituting the values into the formula, we have:

Length of the second train = 35 m/s × 14 s = 490 meters

Therefore, the length of the second train is 490 meters.