Question

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

Answer 1

1) 100 + 80 = 180 км/ч - скорость сближения
2)180 * 1000 : 3600 = 50 м/с - скорость сближения в  м/с
3) 50 * 20 = 1000 м - длина второго поезда

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 for 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 by the passenger in the first train = 20 seconds

To find the length of the second train, we need to convert the speeds from km/h to m/s, as the time is given in seconds.

Converting the speeds: - Speed of the first train = 100 km/h = (100 × 1000) m/3600 s = 1000/36 m/s ≈ 27.78 m/s - Speed of the second train = 80 km/h = (80 × 1000) m/3600 s = 800/36 m/s ≈ 22.22 m/s

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

Length = Speed × Time

Length = (Speed of the second train) × (Time taken for the second train to pass by)

Length = 22.22 m/s × 20 s

Calculating the length:

Length ≈ 444.4 meters

Answer

The length of the second train is approximately 444.4 meters.

Explanation

When two trains are moving towards each other on parallel tracks, the relative speed between them is the sum of their individual speeds. In this case, the relative speed is 100 km/h + 80 km/h = 180 km/h. The second train passes by the passenger in the first train in 20 seconds. By multiplying the relative speed by the time, we can find the distance traveled by the second train, which is equal to its length.