Question

Два поезда двигались по параллельным путям навстречу друг другу , один со скоростью 100 км/ч, а другой со скоростью 80 км/ч. Пассажир, сидевший в первом поезде, заметил, что второй поезд шёл мимо него в течение 20 с, Найди длину второго поезда.

Answer 1

Перейдём в систему отсчёта связанную с пассажиром. 
Тогда в этой системе отсчёта второй поезд будет двигаться мимо пассажира соскоростью 
V=V1+V2=100+80=180 км/ч = 50 м/с 
Длина второго поезда: 
L=V*t=50*20=1000 м

Answer 2

Problem Analysis

We are given two trains moving towards each other on parallel tracks. The first train is traveling at a speed of 100 km/h, while the second train is traveling at a speed of 80 km/h. The passenger in the first train notices that the second train passes by him in 20 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 = Speed × Time

Let's calculate the length of the second train using this formula.

Calculation

Given: - Speed of the first train = 100 km/h - Speed of the second train = 80 km/h - Time taken for the second train to pass the passenger in the first train = 20 seconds

Using the formula Length = Speed × Time, we can calculate the length of the second train.

Length of the second train = Speed of the second train × Time taken for the second train to pass the passenger in the first train

Length = 80 km/h × 20 seconds

Converting the time from seconds to hours: 20 seconds = 20/3600 hours (since 1 hour = 3600 seconds)

Length = 80 km/h × (20/3600) hours

Simplifying the expression: Length = (80 × 20) km / 3600

Length = 1600 km / 3600

Length ≈ 0.4444 km

Therefore, the length of the second train is approximately 0.4444 km.

Answer

The length of the second train is approximately 0.4444 km.