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# Work and energy

The concept of work is strictly defined in physics and is related to the resistance to the force on the given path - work=force x passed path.

Energy

There several kinds of energy and are divided into: kinetic energy (energy of motion) and potential energy (energy stored in the environment). The potential energy is divided into: elastic potential energy and gravitational potential energy.

Kinetic energy

When the work is done force F can be changed; also the path x2-x2 can be long and short; but in the final formula there is only mass and final and starting speed of the body. When the body is moved along the horizontal plane with no friction, that work of the force goes only to raising the speed of the body, then that work is equal to the change of the kinetic energy. If the mass m is move with the speed v, her kinetic energy is 1/2mv2. It means that for the acceleration of the mass m from the state of standstill to the speed v the following energy has to be spent: 1/2mv2. On the other hand , if the body is slowing down under the work of any force, it's kinetic energy is falling.

Potential energy

When stopping the body looses kinetic energy, and it is in some way stored in the environment. The energy stored like this is called potential energy.

Power

In many cases it is necessary to observe the speed at what the work is done, or to say quantity of the work done in the specified period of time. The speed by which the work is done will be called power. The unit for the power is Watt P=w/t.

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