# What is the concept of work?

• tarak20085
In summary, when a person kicks an uncoiled spring, the spring will compress and store energy, which is then used to propel the ball in a certain direction.

#### tarak20085

if I shoot the football, the ball will recive a force in specific direction, and it would follow that direction.
Does the work is done by me when I shooted the ball, or the ball does work when it moves all the period after my shooting ?
the work includes force and displacement , so who does the work ? the ball or me ?
when the ball moves, the force of shooting becomes 0 ? and it stills keep moving because the inertia ? and not because of the work ?

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tarak20085 said:
so who does the work ? the ball or me ?
Usually, if A does positive work on B, then B does negative work on A. But the magnitudes can differ if there is energy dissipation.

• russ_watters
A.T. said:
Usually, if A does positive work on B, then B does negative work on A. But the magnitudes can differ if there is energy dissipation.

tarak20085 said:
These are too many, because you use question marks as commas.

But if there is no force interaction between A & B anymore, then there is no work done between them.

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tarak20085 said:
when the ball moves, the force of shooting becomes 0 ? and it stills keep moving because the inertia ? and not because of the work ?
Yes: work is only being done while the force is being applied.

This is a bit misleading. If there's a pair interaction in the total energy the interaction potential enters only once!

Work is also a transfer of energy. The transfer occurs during the contact (interaction). In the case of the football the kinetic energy of the foot gives some of its energy to the ball (does work on the ball). This energy results, during the contact, in the compression of the surface of the ball . This compression is the results of the work in stretching the surfaces and compressing the gas inside the ball heating the gas as well as heating the surface and temporarily storing energy in the stretched surface. The elastic surface returns some of the energy as the ball begins to move during the period the foot is in contact with the ball.

In the video note the initial contact and hesitation of the ball to move as it is compressed and its subsequent increase in velocity as the surface rebound converting the stored energy into the motion of the ball.

gleem said:
Work is also a transfer of energy. The transfer occurs during the contact (interaction). In the case of the football the kinetic energy of the foot gives some of its energy to the ball (does work on the ball). This energy results, during the contact, in the compression of the surface of the ball . This compression is the results of the work in stretching the surfaces and compressing the gas inside the ball heating the gas as well as heating the surface and temporarily storing energy in the stretched surface. The elastic surface returns some of the energy as the ball begins to move during the period the foot is in contact with the ball.

In the video note the initial contact and hesitation of the ball to move as it is compressed and its subsequent increase in velocity as the surface rebound converting the stored energy into the motion of the ball.

Thank you!
I ve understand what you wanted to explain beside the last chapter
you ve said (as the surface rebound converting the stored energy into the motion of the ball).
Did you mean that the surface stretched in the ball make a work on the total ball ?
moving of the ball when no foot is applying happens because the force of the gaz on the surface

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tarak20085 said:
Did you mean that the stored energy in the ball surface make a work on the total ball ?

Basically, If you kick an uncoiled spring it will compress and store energy imparted by the kick. As the foot follow through the spring expands pushing against the foot. The other end of the spring is unhindered so the expansion produces a force in the direction of the motion of the rest of the spring. The spring (ball) bounces off the foot.

## What is work?

Work is defined as the application of a force over a distance. It is a fundamental concept in physics and is often used to describe the physical or mental effort required to achieve a goal.

## How is work calculated?

Work is calculated by multiplying the force applied by an object by the distance it moves in the direction of the force. The formula for work is W = F x d, where W is work, F is force, and d is distance.

## What are the units of work?

The SI unit for work is the joule (J). It is also commonly measured in newton-meters (N·m). Other units of work include foot-pounds (ft·lb) and calorie (cal).

## What is the difference between work and power?

Work is the amount of energy transferred when a force is applied over a distance. Power, on the other hand, is the rate at which work is done. It is the amount of work done per unit time. The formula for power is P = W/t, where P is power, W is work, and t is time.

## How does work relate to energy?

Work and energy are closely related concepts. Work is the transfer of energy from one object to another. When work is done, energy is either transferred to or from an object, resulting in a change in its energy level. Work and energy have the same unit (joule) and can be converted from one form to another.