Question

грузовой поезд длиной 630 м и экспресс длиной 120 м движуться по двум параллельным путям в одном направлении со скоростями 36км в ч и 72 км в час соответственно . в течение какого времени экспресс будет обгонять грузовой поезд

Answer 1

V1=36мк/ч=10м/с  V2=72мк/ч=20м/с   l1=630  l2=120   t=?
t=(l1+l2)/(V2-V1)=(630+120)/(20-10)=750/10=75[c]

Answer 2

Problem Analysis

We are given the lengths and speeds of a freight train and an express train moving in the same direction on parallel tracks. We need to determine the time it takes for the express train to overtake the freight train.

Solution

To solve this problem, we can use the concept of relative speed. The relative speed is the difference between the speeds of the two trains. The express train needs to cover the length of the freight train to overtake it.

Let's calculate the relative speed and the time it takes for the express train to cover the length of the freight train.

Calculation

The length of the freight train is 630 m, and its speed is 36 km/h. The length of the express train is 120 m, and its speed is 72 km/h.

First, let's convert the speeds to m/s for consistency: - Speed of the freight train: 36 km/h = (36 * 1000) m / (60 * 60) s = 10 m/s - Speed of the express train: 72 km/h = (72 * 1000) m / (60 * 60) s = 20 m/s

The relative speed of the express train with respect to the freight train is the difference between their speeds: Relative speed = Speed of the express train - Speed of the freight train = 20 m/s - 10 m/s = 10 m/s

To overtake the freight train, the express train needs to cover the length of the freight train, which is 630 m.

The time it takes for the express train to cover the length of the freight train can be calculated using the formula: Time = Distance / Speed

Substituting the values: Time = 630 m / 10 m/s = 63 s

Answer

The express train will overtake the freight train in 63 seconds.

Explanation

The express train is moving at a higher speed than the freight train. Therefore, it will gradually catch up with and overtake the freight train. The time it takes for the express train to overtake the freight train is 63 seconds.

Please let me know if you need any further clarification.