Potential & Kinetic Energy

All energy can be in one of two states:  potential energy or kinetic energy.
Energy can be transferred from potential to kinetic and between objects.
Potential energy is stored energy--energy ready to go.  A lawn mower filled with gasoline, a car on top of a hill, and students waiting to go home from school are all examples of potential energy.
Gravitational potential energy is the energy possessed by a body because of its elevation (height) relative to a lower elevation, that is, the energy that could be obtained by letting it fall to a lower elevation.  For example, water at the top of a waterfall or stored behind a dam at a hydroelectric plant has gravitational potential energy.

Most of the energy under our control is in the form of potential energy.  Potential energy can be viewed as motion waiting to happen.  When the motion is needed, potential energy can be changed into one of the six forms of kinetic energy.
Kinetic energy is energy at work.  A lawn mower cutting grass, a car racing down a hill, and students running home from school are examples of kinetic energy.  So is the light energy emitted by lamps.  Even electrical energy is kinetic energy.  Whenever we use energy to do work, it is in the kinetic state.

The kinetic energy of an object is the energy which it possesses due to its motion.
In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is ½ mv². In relativistic mechanics, this is only a good approximation when v is much less than the speed of light.

In physics, potential energy is the energy of a body or a system with respect to the position of the body or the arrangement of the particles of the system.

The SI unit of measure for energy and work is the Joule (symbol J).
Formula:
PE=mgh
where:
PE=Potential Energy
m=mass
g=acceleration due to gravity
h=height

Energy and its Many Forms & Energy Transformation

The meaning of energy and it’s seven forms.

Energy
Energy is the ability to cause and change. The capacity to perform work.  An exertion of force.  In all, it is the ability to  make something happen. Energy forms are either kinetic or potential.  Potential energy is stored energy and the energy of position while kinetic energy is motion
Seven forms of  energy:
1. Nuclear Energy
Nuclear energy is stored in  the nucleus of an atom.  The energy that holds the nucleus together.  The energy can be released when  the  nuclei are combined or split apart.
 

2. Radiant Energy
Radiant energy is the electromagnetic energy that travels in  transverses waves.  Radiant energy includes visible light, x-rays, gamma rays amd radio waves.  Light is one type of radiant energy.  Solar energy is an example of radiant energy.
Solar
 
-o-
Radio Waves

3. Electrical Energy
Electrical energy is  the movement of electrical charges.  Everything is made of tiny particles called atoms.  Electrical charges moving  through a wire is called electricity.  Lighting is an example of electrical energy.
 

4. Chemical Energy
Chemical energy is energy stored in the bonds of atoms and molecules.  It is the energy that holds these particles together.  Examples are biomass, petroleum, natural gas and propane.


5. Mechanical Energy
Mechanical energy relates to the movement of objects or its position in relation to gravity.
 
6. Sound Energy
Sound energy is the movement of energy through substances in longitudinal waves.  Sound is produced when a force causes an object or substance to vibrate.  The energy is transferred through  the substance in a wave.
Acoustic Speakers
 
-o-
Sonar

7. Thermal Energy  
Thermal energy is the internal energy  in substances.  The vibration and movement of the atoms and molecules within substances.  Geothermal energy is an example of thermal energy.
Geothermal Plant

 For further reading on renewable energy, please read “Bloom Box – The Holy Grail of Renewable Energy“

Energy Transformation:

Energy transformation is when energy changes into another form. In physics, the term energy describes the capacity to produce certain changes within a system, without regard to limitations in transformation imposed by entropy.

Examples of sets of energy conversions in machines

For instance, a coal-fired power plant involves these energy transformations:

1. Chemical energy in the coal converted to thermal energy
2. Thermal energy converted to kinetic energy in steam
3. Kinetic energy converted to mechanical energy in the turbine
4. Mechanical energy of the turbine converted to electrical energy, which is the ultimate output

In such a system, the last step is almost perfectly efficient, the first and second steps are fairly efficient, but the third step is relatively inefficient. The most efficient gas-fired electrical power stations can achieve 50% conversion efficiency. Oil and coal fired stations achieve less.
In a conventional automobile, these energy transformations are involved:

1. Potential energy in the fuel converted to kinetic energy of expanding gas via combustion
2. Kinetic energy of expanding gas converted to linear piston movement
3. Linear piston movement converted to rotary crankshaft movement
4. Rotary crankshaft movement passed into transmission assembly
5. Rotary movement passed out of transmission assembly
6. Rotary movement passed through differential
7. Rotary movement passed out of differential to drive wheels
8. Rotary movement of drive wheels converted to linear motion of the vehicle.

[edit] Other energy conversions

There are many different machines and transducers that convert one energy form into another. A short list of examples follows:

• Thermoelectric (Heat → Electric energy)
• Geothermal power (Heat→ Electric energy)
• Heat engines, such as the internal combustion engine used in cars, or the steam engine (Heat → Mechanical energy)
• Ocean thermal power (Heat → Electric energy)
• Hydroelectric dams (Gravitational potential energy → Electric energy)
• Electric generator (Kinetic energy or Mechanical work → Electric energy)
• Fuel cells (Chemical energy → Electric energy)
• Battery (electricity) (Chemical energy → Electric energy)
• Fire (Chemical energy → Heat and Light)
• Electric lamp (Electric energy → Heat and Light)
• Microphone (Sound → Electric energy)
• Wave power (Mechanical energy → Electric energy)
• Windmills (Wind energy → Electric energy or Mechanical energy)
• Piezoelectrics (Strain → Electric energy)
• Acoustoelectrics (Sound → Electric energy)
• Friction (Kinetic energy → Heat)
• Electric Energy into Thermal Energy Example:Heater
• light energy into electrical energy example chocolates