Sunday, January 27, 2013

Energy


What is energy?

Energy is the enforcement that allows work to occur. Therefore, whenever there is work, there is energy.

There are a variety of diverse forms of energy. The forms of energy are chemical energy, thermal energy, sound energy, light energy, electrical energy, and mechanical energy.

-       Chemical energy is the energy is an energy contained within food, your body, and fuel.
o   Example: The energy contained in food


-       Thermal energy is the energy associated with the random motion of particles.
o   Example: Rubbing your hands together to create heat


-       Sound energy is the energy produced by the radiation of air particles around a sound source.
o   Example: A person playing the clarinet


-       Light energy is the energy produced by the radiation of electromagnetic waves.
o   Example: Flashlight


-       Electrical energy is the energy produced by electric charges that move through cables.
o   Example: Laptop charger


-       Nuclear energy is the energy released from the reaction of the nucleus of radioactive matters.
o   Example: Nuclear bomb


-       Mechanical energy is the energy associated with motion.
o   Potential energy is in occurrence when the object is not touching the surface.
§  Example: Chandelier


o   Kinetic energy is present when an object is in motion.
§  Example: A moving car





Sunday, January 20, 2013

Work


What is work?

Work is the result of displacement of an object with force.

In our daily lives, everyone performs work whether intentional or not. For instance, during midday when the sun is in the sky, any individual would wear sunglasses to prevent eye damage from occurring. The act of lifting the sunglasses from its case is considered as work since the sunglasses are being moved from the case to the eye area. So there is force and displacement given during this performance.





What is not work?

There is no work if the force doesn’t cause any movement on the object, or if the force and the displacement appear in opposite directions. In the event that this happens, the work will be zero.

As mentioned before, the process in placing the sunglasses on is regarded as work. However, it is not work when wearing the sunglasses due to the fact that there is no movement/displacement even though there is force in the performance.



Unit of measurement

·      Work: Joules (J)
·      Force: Newtons (N)
·      Displacement: Meters (m)

Formula of work
W = F d
·      W = Work
·      F = Force
·      d = Displacement

The formula above states that the force applied on an object multiplied by the displacement of the same object is work. However, in some cases there could be two forces acted on one object going in the same direction. In this occurrence, you must add the two forces together then multiply the result by the displacement. On the other hand, if the two forces proceed in opposite directions you must subtract the forces.

Examples
a.     A customer is pushing a cart at 11N down a straight 8m aisle while shopping in a grocery store, what is the work?


Answer:
W = F d
W = 11 x 8
W = 88 J

b.     What is the work if two people wanted to move a table 3m away? The first person pushes at 18N and the other at 13N?

Answer:
W = F d
W = (18 + 13) x 3
W = 31 x 3
W = 93