Question

2.5. Скорость поезда, движущегося на подъем с ускорением 0,2 м/с², уменьшается от 72 до 54 км/ч. Определите время подъема.С дано и решением, пожалуйста помогите)))))

Answer 1

vo=72км/ч= 20м/с

v1= 54км/ч = 15м/с

a= -0.2м/с² (т.к. при движении уменьшается скорость)

a=(v1-vo)/t - из опредедения ускорения =>

t= (v1-vo)/a

t= (15м/с - 20м/с)/(-0.2м/с²) = 25с

Ответ: время подъёма равно 25 секунд.

Answer 2

Problem Analysis

We are given the following information: - The train is moving uphill with an acceleration of 0.2 m/s². - The speed of the train decreases from 72 km/h to 54 km/h.

We need to determine the time it takes for the train to climb the hill.

Solution

To solve this problem, we can use the equations of motion. The equation that relates initial velocity (v₀), final velocity (v), acceleration (a), and time (t) is:

v = v₀ + at

In this case, the initial velocity (v₀) is 72 km/h, the final velocity (v) is 54 km/h, and the acceleration (a) is 0.2 m/s². We need to convert the velocities from km/h to m/s before plugging them into the equation.

Converting the velocities: - 72 km/h = 20 m/s - 54 km/h = 15 m/s

Now we can plug the values into the equation and solve for time (t):

15 m/s = 20 m/s + 0.2 m/s² * t

Simplifying the equation: 15 m/s - 20 m/s = 0.2 m/s² * t

-5 m/s = 0.2 m/s² * t

Dividing both sides of the equation by 0.2 m/s²: t = -5 m/s / 0.2 m/s²

t = -25 s

The negative sign indicates that the train is slowing down, so we need to take the absolute value of the time. Therefore, the time it takes for the train to climb the hill is 25 seconds.

Answer

The time it takes for the train to climb the hill is 25 seconds.