Question

Камень брошен вертикально вверх со скоростью 20 м/с. Масса камня 200 г, скорость в момент падения на землю равна 10 м/с. Какова работа силы сопротивления воздуха?

Answer 1

Calculation of Work Done by Air Resistance

To calculate the work done by air resistance, we need to determine the change in kinetic energy of the stone as it falls from its maximum height to the ground.

Given: - Initial velocity of the stone when thrown vertically upward: 20 m/s- Mass of the stone: 200 g (or 0.2 kg) - Velocity of the stone when it hits the ground: 10 m/s To find the work done by air resistance, we can use the equation:

Work = Change in Kinetic Energy

The change in kinetic energy can be calculated as:

Change in Kinetic Energy = (1/2) * mass * (final velocity^2 - initial velocity^2)

Substituting the given values into the equation, we have:

Change in Kinetic Energy = (1/2) * 0.2 kg * (10 m/s)^2 - (20 m/s)^2

Simplifying the equation, we get:

Change in Kinetic Energy = (1/2) * 0.2 kg * (100 m^2/s^2 - 400 m^2/s^2)

Change in Kinetic Energy = (1/2) * 0.2 kg * (-300 m^2/s^2)

Change in Kinetic Energy = -30 J

The negative sign indicates that the kinetic energy of the stone decreases as it falls due to the work done by air resistance.

Therefore, the work done by air resistance is -30 Joules.