Energy

     You can do your activity if you have energy. Beside that, horse can attract cart because the horse has energy. Energy is defined as ability to perform work. Energy unit in International Standard is Joule (J). The other unit for energy is calorie, 1 joule = 0.24 calorie.

      Energy has several forms. The forms of energy can alter. How this happen? concern the following explanation.

1. Energy Form
    Viewed from the source, energy has various forms. The forms of energy are potential energy, kinetic energy chemical energy, heat energy, electrical energy, sound energy, nuclear energy and radiation energy. Explanation of the energy forms as follow.

a.  Potential energy
     Potential energy is energy contained in motionless object. This energy also called idle energy. For
example, there is an object in certain height and pulled or pushed spring. If the object is released, it will make a work. The work can be in motion. (Included in the mechanical energy)
b.  Kinetic energy
     Kinetic energy is energy owned by any object when it is moving. For example, people running, a car running in medium speed, rotating object, and moving cart. When moving, object have energy. Because kinetic energy is owned by moving object, the value of energy is depend on mass and velocity. (Included in the mechanical energy)
c.  Chemical energy
     Chemical energy is energy resulted as the output of chemical reaction. Battery, food, and fuel generally composed of chemical compound stored chemical energy.
d.  Heat energy
     Heat energy is energy generated from friction between two objects or from objects that produce heat. Heat energy is energy the most energy you find in environment. For example, when you are exposing your clothes under the sun, you are utilizing solar energy, when you are cooking, and when you are utilizing heat energy derived from coal.
e.  Electrical energy
     Electrical energy is energy stored in electrical flow (moving load). This electrical energy is usually utilized by human being. Several electrical tools use electrical energy. For example, it electrical stove, electrical iron, rice cooker, radio, and television.
f.   Sound energy
     Sound energy is energy which comes from the vibration of an object. Sound energy is contained in all sound types. For example, people who are talking, exploding bomb, and thunder.
g.  Nuclear energy
     Nuclear energy is energy resulted by nuclear fission.
h.   Radiation energy
      Radiation energy is energy obtained from the light of a lighting material.
 3. Change of Energy

4. Mechanical Energy

      Mechanical energy is the energy possessed by an object related to the motion. Mechanical energy comprises potential and kinetic energy.

a.    Potential Energy
       Potential energy is energy owned by an object due to its place. A coconut hanging  in its tall tree has potential energy, why ? Potential energy of any object is bigger when the position is higher. Mathematically, the formula is :

                          E_p = m. g. h

Note :

E_p : potential energy, the unit is joule (J)

m : mass of object, the unit is kilogram (kg)

g : acceleration of gravity, the unit is m/s²

h : height of object from ground, the unit is meter (m)

     Energy unit in International Standard is joule (J). While in CGS system, the unit is erg. The other example of potential energy is in spring.

b.  Kinetic Energy
     Kinetic energy is energy owned by an object due to its motion. In billiard, we often see a ball hit using stick will move and hit the other ball. What happens with the ball? in fact, the ball also move because of the motion of the first ball. This means that moving ball is able to do work or has energy. The energy is called kinetic energy. Value of kinetic energy of any object is depending on its mass and speed. mathematically, the formula is :

                                   E_k = ½. m. v²

 Note :

 E_{k : kinetic energy of subject, the unit in joule (J)}

_{m : mass of object, the unit is kilogram (kg)}

_{v : velocity of any object, the unit is m/s} 

_{4. Conservation Laws of Energy}

        Note the ball is bounced. At first, the ball was on the point a, storing the kinetic energy and potential energy greatest zero because the ball has not moved. When the ball bounced start, then began to decrease its kinetic energy and potential energy increases as the speed of the increase. When the ball is at point b, the ball will lose kinetic energy and potential energy saving only. As the ball begins to fall, the same thing happen again. Potential energy decreases, while the kinetic energy will increase. So the kinetic energy is transformed into potential energy and conversely. The amount of potential energy and kinetic energy each time is fixed. The amount of energy is called mechanical energy_.

                                                         E_m = E_p + E_k

  

1. At position a, the entire mechanical energy is kinetic energy, so that:     

            E_m = E_p = m . g . h

2. At position B, the entire mechanical energy is the sum of potential energy and kinetic energy, so that:

          E_m = E_p + E_k

                = m. g. h + ½. m. v²

3. At position c, the entire mechanical energy is potential energy, so that :

          E_m = E_k = ½. m. v²

      If no outside force influences, then the potential energy falling objects become smaller and greater kinetic energy. Large reduction in the potential energy equal to the kinetic energy onset. The conservation laws of energy of energy states that "energy can not be created, can only be changed into other forms of energy", the mechanical energy is also constant (conserved) energy.

"That is about Energy, please give your comment"