Question

Мальчик бросил мяч массой 100 г вертикально вверх и поймал его в точке бросания. При движении вверх мяч достиг высоты 5 м. Вычислите работу силы тяжести, действующей на мяч, при движении мяча: а) вверх; б) вниз; в) за все время полета.Помогите, заранее благодарю!)

Answer 1

Дано:

m = 100 г = 0,1 кг, h = 5 м.

Найти: А1 ,А2 ,А3

Решение.

Ответ: А1 = -5 Дж, А 2 = 5 Дж, А3 = 0.

Answer 2

Calculation of Work Done by Gravity on the Ball

To calculate the work done by the force of gravity on the ball during its motion, we need to consider the different phases of its trajectory: upward motion, downward motion, and the entire flight.

# a) Work Done by Gravity During Upward Motion

During the upward motion of the ball, the work done by the force of gravity is negative because the displacement is in the opposite direction of the force. The work done by gravity can be calculated using the formula:

Work = Force x Displacement x cos(theta)

In this case, the force of gravity is equal to the weight of the ball, which can be calculated using the formula:

Weight = mass x acceleration due to gravity

Given that the mass of the ball is 100 g (0.1 kg) and the acceleration due to gravity is approximately 9.8 m/s^2, we can calculate the weight of the ball:

Weight = 0.1 kg x 9.8 m/s^2 = 0.98 N

The displacement during the upward motion is equal to the height reached by the ball, which is 5 m.

Using these values, we can calculate the work done by gravity during the upward motion:

Work = -0.98 N x 5 m x cos(180 degrees) = -4.9 J

Therefore, the work done by the force of gravity during the upward motion of the ball is -4.9 Joules.

# b) Work Done by Gravity During Downward Motion

During the downward motion of the ball, the work done by the force of gravity is positive because the displacement is in the same direction as the force. The work done by gravity can be calculated using the same formula as above:

Work = Force x Displacement x cos(theta)

In this case, the force of gravity is still equal to the weight of the ball, which is 0.98 N. The displacement during the downward motion is also 5 m.

Using these values, we can calculate the work done by gravity during the downward motion:

Work = 0.98 N x 5 m x cos(0 degrees) = 4.9 J

Therefore, the work done by the force of gravity during the downward motion of the ball is 4.9 Joules.

# c) Work Done by Gravity During the Entire Flight

To calculate the work done by gravity during the entire flight of the ball, we need to consider both the upward and downward motions. Since the work done during the upward motion is negative and the work done during the downward motion is positive, the total work done by gravity is the sum of these two values:

Total Work = Work Upward + Work Downward

Total Work = -4.9 J + 4.9 J = 0 J

Therefore, the work done by the force of gravity during the entire flight of the ball is 0 Joules.

Please note that the calculations above are based on the assumption that there is no air resistance or other external forces acting on the ball during its motion.