Question

Определить кинетическую энергию тела массой 1 кг, брошенного горизонтально со скоростью 20 м/с, в конце четвертой секунды его полета. Написать полное решение

Answer 1

M=1кг
Vx=20 м/с
g=10 м/с²
Ek-?
Ek=mV²/2
Необходимо найти скорость V в конце четвёртой секунды.
Vy=gt, Vy=10*4=40 м/с
V²=V²x +V²y, V²=20²+40²= 2000, V=√2000= 44,7 м/с
Еk=1кг* (44,7 м/с)²/2 = 1000 Дж= 1кДж
Ответ: 1 кДж

Answer 2

Кинетическая энергия в начале
Ек0 = mv^2/2= 200 Дж
За четыре секунды тело опустится на высоту
h = gt^2/2= 80 м
при этом его потенциальная энергия
Еп= mgh= 800 Дж
перейдет в кинетическую .
Суммарная кинетическая энергия через четыре секунды
Ек=Ек0+Еп= 1000Дж

Answer 3

Problem Statement

We are given a body with a mass of 1 kg that is thrown horizontally with a velocity of 20 m/s. We need to determine the kinetic energy of the body at the end of the fourth second of its flight.

Solution

To solve this problem, we need to find the height of the body at the end of the fourth second and then calculate its kinetic energy using the formula for kinetic energy.

# Step 1: Finding the height of the body

The height of the body can be calculated using the formula for vertical motion under constant acceleration:

h = h0 + v0t + (1/2)gt^2

Where: - h is the height of the body at time t - h0 is the initial height (which is 0 in this case as the body is thrown horizontally) - v0 is the initial vertical velocity (which is 0 in this case as the body is thrown horizontally) - t is the time (which is 4 seconds in this case) - g is the acceleration due to gravity (which is approximately 9.8 m/s^2)

Substituting the given values into the formula, we can calculate the height of the body at the end of the fourth second.

# Step 2: Calculating the kinetic energy

The kinetic energy of an object can be calculated using the formula:

KE = (1/2)mv^2

Where: - KE is the kinetic energy - m is the mass of the object - v is the velocity of the object

Substituting the given values into the formula, we can calculate the kinetic energy of the body at the end of the fourth second.

Let's calculate the height and kinetic energy using the given information.

# Step 1: Finding the height of the body

Using the formula for vertical motion, we can calculate the height of the body at the end of the fourth second:

h = h0 + v0t + (1/2)gt^2

Since the body is thrown horizontally, the initial height (h0) and initial vertical velocity (v0) are both 0. Substituting the values into the formula, we get:

h = 0 + 0 * 4 + (1/2) * 9.8 * (4^2)

Simplifying the equation, we have:

h = 0 + 0 + 0.5 * 9.8 * 16

Calculating the expression, we find:

h = 78.4 meters

Therefore, the height of the body at the end of the fourth second is 78.4 meters.

# Step 2: Calculating the kinetic energy

Using the formula for kinetic energy, we can calculate the kinetic energy of the body at the end of the fourth second:

KE = (1/2)mv^2

Substituting the given values into the formula, we get:

KE = (1/2) * 1 * (20^2)

Simplifying the equation, we have:

KE = 0.5 * 1 * 400

Calculating the expression, we find:

KE = 200 Joules

Therefore, the kinetic energy of the body at the end of the fourth second is 200 Joules.

Answer

The kinetic energy of a body with a mass of 1 kg, thrown horizontally with a velocity of 20 m/s, at the end of the fourth second of its flight is 200 Joules. The height of the body at that time is 78.4 meters.

Please let me know if you need any further clarification.