Question

Автомобиль начал двигаться равноускоренно и прошел 25 м пути за 5 с.За какое время он пройдет 400 м пути,считая от начала движения?

Answer 1

S=a*t^2/2 => a=2s/t^2=2*25/5^2=2 м/с^2
$\\ t= \sqrt{ \frac{2s}{a} }= \sqrt{ \frac{2*400}{2} }=20 c$ 
проверьте!

Answer 2

Problem Analysis

We are given that a car starts moving with constant acceleration and covers a distance of 25 m in 5 s. We need to determine the time it will take for the car to cover a distance of 400 m from the start.

Solution

To solve this problem, we can use the equations of motion for uniformly accelerated motion. The equation that relates distance, initial velocity, time, and acceleration is:

s = ut + (1/2)at^2

where: - s is the distance traveled, - u is the initial velocity, - t is the time taken, and - a is the acceleration.

In this case, the car starts from rest, so the initial velocity (u) is 0. We are given that the car covers a distance of 25 m in 5 s. We can use this information to find the acceleration (a). Once we have the acceleration, we can use it to find the time (t) it will take for the car to cover a distance of 400 m.

Let's calculate the acceleration first.

Calculation

Given: - Distance covered (s) = 25 m - Time taken (t) = 5 s - Initial velocity (u) = 0

Using the equation s = ut + (1/2)at^2, we can rearrange it to solve for acceleration (a):

a = 2(s - ut) / t^2

Substituting the given values:

a = 2(25 - 0 * 5) / 5^2

Simplifying:

a = 2(25) / 25

a = 2 m/s^2

Now that we have the acceleration, we can use it to find the time it will take for the car to cover a distance of 400 m.

Using the same equation s = ut + (1/2)at^2, we can rearrange it to solve for time (t):

t = sqrt(2s / a)

Substituting the given values:

t = sqrt(2 * 400 / 2)

Simplifying:

t = sqrt(400)

t = 20 s

Therefore, it will take the car 20 seconds to cover a distance of 400 meters from the start.

Answer

The car will take 20 seconds to cover a distance of 400 meters from the start, assuming it starts from rest and moves with constant acceleration.