Question

Отходящий от станции поезд в течение первых 20 с двигался прямолинейно и равноускоренно.За третью секунду от начала движения поезд прошел 2м.какое перемещение совершил поезд за пятнадцатую секунду движения?Чему была равна скаорость поезда в конце двадцатой секунды движения?ПОМОГИТЕ!!!

Answer 1

Дано: ВС=2м Решение: 
t=1c OA:BC=1:5 
OA-? OA:2м=1:5 
а-? 5*ОА=2м 
ОА=2м/5м=0,4м 
ОА= (а(х))*((1с)в квадрате)/2 
а=2*ОА/(1с)кв=(2*0,4м)/1с(кв)=0,8м/с(кв) 
Ответ:ОА=0,4;а=0,8м/с(кв)

Answer 2

Problem Analysis

We are given that a train moves in a straight line with constant acceleration for the first 20 seconds. We are also given that the train travels 2 meters in the third second. We need to find the displacement of the train during the fifteenth second and the velocity of the train at the end of the twentieth second.

Solution

To solve this problem, we can use the equations of motion for uniformly accelerated motion. The equations we will use are:

1. Displacement: s = ut + (1/2)at^2 2. Velocity: v = u + at

where: - s is the displacement - u is the initial velocity - t is the time - a is the acceleration - v is the final velocity

Let's calculate the displacement of the train during the fifteenth second first.

Calculation: Displacement during the Fifteenth Second

We are given that the train travels 2 meters in the third second. Let's assume the initial velocity of the train is u and the acceleration is a.

Using the equation of motion for displacement, we can write:

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

For the third second, when t = 3 seconds, the displacement is 2 meters:

2 = 3u + (1/2)a(3^2)

Simplifying the equation:

2 = 3u + (9/2)a

Now, let's calculate the displacement during the fifteenth second, when t = 15 seconds.

Using the same equation of motion for displacement:

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

Substituting the values:

s = 15u + (1/2)a(15^2)

We can solve this equation to find the displacement during the fifteenth second.

Calculation: Velocity at the End of the Twentieth Second

To find the velocity at the end of the twentieth second, we can use the equation of motion for velocity:

v = u + at

Substituting the values:

v = u + a(20)

We can solve this equation to find the velocity at the end of the twentieth second.

Let's calculate the displacement during the fifteenth second and the velocity at the end of the twentieth second.

Calculation: Displacement during the Fifteenth Second

Using the equation derived earlier:

2 = 3u + (9/2)a

Simplifying the equation:

4 = 6u + 9a

Calculation: Velocity at the End of the Twentieth Second

Using the equation derived earlier:

v = u + a(20)

Simplifying the equation:

v = u + 20a

Now, we have two equations with two unknowns (u and a). We can solve these equations simultaneously to find the values of u and a.