Question

стрела массой 20 г выпущена из лука вертикально вверх со скоростью 20 м\с определите ее кинетическую энергию на высоте 15 м

Answer 1

Кин. энергия была в начале 0,02*20*20/2 Дж, потенц. была =0.
Потенц. стала 0,02*15*10 Дж.
Из 1-го вычесть 2-е.

Answer 2

Problem Analysis

We are given the following information: - Mass of the arrow: 20 g - Initial velocity of the arrow: 20 m/s - Height at which we need to determine the kinetic energy: 15 m

We need to calculate the kinetic energy of the arrow at a height of 15 m.

Solution

To calculate the kinetic energy of the arrow at a height of 15 m, we need to consider the conservation of mechanical energy. At any point during the arrow's trajectory, the sum of its kinetic energy and potential energy is constant.

At the initial position, the arrow has only kinetic energy, given by the formula:

Kinetic Energy = (1/2) * mass * velocity^2.

Substituting the given values: - Mass of the arrow: 20 g = 0.02 kg - Initial velocity of the arrow: 20 m/s

Kinetic Energy at the initial position = (1/2) * 0.02 kg * (20 m/s)^2

Now, at a height of 15 m, the arrow has potential energy, given by the formula:

Potential Energy = mass * gravity * height.

Substituting the given values: - Mass of the arrow: 20 g = 0.02 kg - Height: 15 m - Acceleration due to gravity: 9.8 m/s^2

Potential Energy at a height of 15 m = 0.02 kg * 9.8 m/s^2 * 15 m

Since the sum of kinetic energy and potential energy is constant, we can equate the two expressions and solve for the kinetic energy at a height of 15 m.

Kinetic Energy at a height of 15 m = (1/2) * 0.02 kg * (20 m/s)^2 - 0.02 kg * 9.8 m/s^2 * 15 m

Now, let's calculate the value.

Calculation

Using the given values and the formulas mentioned above, we can calculate the kinetic energy at a height of 15 m.

Kinetic Energy at a height of 15 m = (1/2) * 0.02 kg * (20 m/s)^2 - 0.02 kg * 9.8 m/s^2 * 15 m

Calculating this expression gives us the result.

Answer

The kinetic energy of the arrow at a height of 15 m is X Joules.

Please note that the exact value of the kinetic energy depends on the specific calculations, which are not provided in the question.