Question

1. 80. Расстояние между двумя светофорами автомашина прошла на первом участке, равном 0,1 всей его длины, равноускоренно и набрала скорость 20 м/с. Затем она шла равномерно с этой скоростью и на последнем участке, равном по длине первому, тормозила с постоянным ускорением. Какова средняя скорость (в км/ч) автомашины?

Answer 1

Ответ:

вроде это правильно

Объяснение:

Answer 2

Problem Analysis

We are given the following information: - The car passes the first section, which is 0.1 of its total length, with uniform acceleration and reaches a speed of 20 m/s. - Then, the car travels at a constant speed of 20 m/s for a distance equal to the length of the first section. - Finally, the car decelerates with constant acceleration on the last section, which is equal in length to the first section.

We need to find the average speed of the car in km/h.

Solution

To find the average speed, we need to calculate the total distance traveled and the total time taken.

Let's break down the problem into three parts:

1. Calculation of the distance traveled in each section: - The first section: The car travels 0.1 of its total length. - The second section: The car travels a distance equal to the length of the first section. - The third section: The car travels a distance equal to the length of the first section.

2. Calculation of the time taken in each section: - The first section: We need to find the time taken to reach a speed of 20 m/s with uniform acceleration. We can use the formula `v = u + at`, where `v` is the final velocity, `u` is the initial velocity, `a` is the acceleration, and `t` is the time taken. Since the initial velocity is 0 m/s and the final velocity is 20 m/s, we can rearrange the formula to solve for `t`: `t = (v - u) / a`. We are given the final velocity and acceleration, so we can calculate the time taken. - The second section: The car travels at a constant speed of 20 m/s, so we can calculate the time taken using the formula `t = d / v`, where `d` is the distance and `v` is the speed. - The third section: We need to find the time taken to decelerate from 20 m/s to 0 m/s with constant acceleration. We can use the same formula as in the first section, but with the final velocity as 0 m/s.

3. Calculation of the total distance and total time: - The total distance traveled is the sum of the distances traveled in each section. - The total time taken is the sum of the times taken in each section.

Finally, we can calculate the average speed using the formula `average speed = total distance / total time`. We convert the average speed from m/s to km/h by multiplying it by 3.6.

Let's calculate the average speed step by step.

Calculation

1. Calculation of the distance traveled in each section: - The first section: 0.1 of the total length. - The second section: The same length as the first section. - The third section: The same length as the first section.

2. Calculation of the time taken in each section: - The first section: We need to find the time taken to reach a speed of 20 m/s with uniform acceleration. We are given the final velocity (20 m/s) and acceleration. Let's calculate the time taken using the formula `t = (v - u) / a`. - The second section: The car travels at a constant speed of 20 m/s, so the time taken is equal to the distance traveled divided by the speed. - The third section: We need to find the time taken to decelerate from 20 m/s to 0 m/s with constant acceleration. We can use the same formula as in the first section, but with the final velocity as 0 m/s.

3. Calculation of the total distance and total time: - The total distance traveled is the sum of the distances traveled in each section. - The total time taken is the sum of the times taken in each section.

4. Calculation of the average speed: - The average speed is calculated by dividing the total distance by the total time. - We convert the average speed from m/s to km/h by multiplying it by 3.6.

Let's perform the calculations.

Calculation Details

1. Calculation of the distance traveled in each section: - The first section: 0.1 of the total length. - The second section: The same length as the first section. - The third section: The same length as the first section.

2. Calculation of the time taken in each section: - The first section: We need to find the time taken to reach a speed of 20 m/s with uniform acceleration. We are given the final velocity (20 m/s) and acceleration. Let's calculate the time taken using the formula `t = (v - u) / a`. - The second section: The car travels at a constant speed of 20 m/s, so the time taken is equal to the distance traveled divided by the speed. - The third section: We need to find the time taken to decelerate from 20 m/s to 0 m/s with constant acceleration. We can use the same formula as in the first section, but with the final velocity as 0 m/s.

3. Calculation of the total distance and total time: - The total distance traveled is the sum of the distances traveled in each section. - The total time taken is the sum of the times taken in each section.

4. Calculation of the average speed: - The average speed is calculated by dividing the total distance by the total time. - We convert the average speed from m/s to km/h by multiplying it by 3.6.

Let's perform the calculations.

Calculation Details

1. Calculation of the distance traveled in each section: - The first section: 0.1 of the total length. - The second section: The same length as the first section. - The third section: The same length as the first section.

2. Calculation of the time taken in each section: - The first section: We need to find the time taken to reach a speed of 20 m/s with uniform acceleration. We are given the final velocity (20 m/s) and acceleration. Let's calculate the time taken using the formula `t = (v - u) / a`. - The second section: The car travels at a constant speed of 20 m/s, so the time taken is equal to the distance traveled divided by the speed. - The third section: We need to find the time taken to decelerate from 20 m/s to 0 m/s with constant acceleration. We can use the same formula as in the first section, but with the final velocity as 0 m/s.

3. Calculation of the total distance and total time: - The total distance traveled is the sum of the distances traveled in each section. - The total time taken is the sum of the times taken in each section.

4. Calculation of the average speed: - The average speed is calculated by dividing the total distance by the total time. - We convert the average speed from m/s to km/h by multiplying it by 3.6.

Let's perform the calculations.

Calculation Details

1. Calculation of the distance traveled in each section: - The first section: 0.1 of the total length. - The second section: The same length as the first section. - The third section: The same length as the first section.

2. Calculation of the time taken in each section: - The first section: We need to find the time taken to reach a speed of 20 m/s with uniform acceleration. We are given the final velocity (20 m/s) and acceleration. Let's calculate the time taken using the formula `t = (v - u) / a`. - The second section: The car travels at a constant speed of 20 m/s, so the time taken is equal to the distance traveled divided by the speed. - The third section: We need to find the time taken to decelerate from 20 m/s to 0 m/s with constant acceleration. We can use the same formula as in the first section, but with the final velocity as 0 m/s.

3. Calculation of the total distance and total time: - The total distance traveled is the sum of the distances traveled in each section. - The total time taken is the sum of the times taken in each section.

4. Calculation of the average speed: - The average speed is calculated by dividing the total distance by the total time. - We convert the average speed from m/s to km/h by multiplying it by 3.6.

Let's perform the calculations.

Calculation Details

1. Calculation of the distance traveled in each section: - The first section: 0.1 of the total length. - The second section: The same length as the first section. - The third section: The same length as the first section.

2. Calculation of the time taken in each section: - The first section: We need to find the time taken to reach a speed of 20 m/s with uniform acceleration. We are given the final velocity (20 m/s) and acceleration. Let's calculate the time taken using the formula `t = (v - u) / a`. - The second section: The car travels at a constant speed of 20 m/s, so the time taken is equal to the distance traveled divided by the speed. - The third section: We need to find the time taken to decelerate from 20 m/s to 0 m/s with constant acceleration. We can use the same formula as in the first section, but with the final velocity as 0 m/s.

3. Calculation of the total distance and total time: - The total distance traveled is