How do we represent change in energy? How is it calculated?

Question

How do we represent change in energy? How is it calculated?

Answer 1

You can represent energy change by an Energy Vector Diagram.

Starting energy --> Ending Energy 1 + Ending Energy 2.. + HEAT

To calculate the energy... work out the amount of energy BEFORE the interaction...  and then work out the Energy after the interaction.  They should be EQUAL.

As for the types of energies...

Each type of energy has a different formula to work out.

eg: Graviation Potential Energy = mgh

Kinetic energy = (1/2)mv^2

etc...

  

Answer 2

change in energy can be represented as "delta E" where delta is represented by a small triangle and E is the energy ur representing.

its calculated by subtracting the energy of a system in its initial stage from its energy in its final stage.

if this difference is negative, it means that the system has released energy. if its positive then the system has absorbed or consumed energy

Answer 3

Energy is measured in work done over a certain amount of time.

Energy is calculated by seeing what it takes to move mass over a distance; horsepower, foot-pound, meter-kilogram watts and torque are just a few units we use to measure the work done.  All you need to do is add the component of time; like how many calories burned per hour of activity, electricity is sold by the kilowatt hour.

Change in energy would be a positive or negative value of an unit of energy.

Here are some units of energy over time:  http://en.wikipedia.org/wiki/List_of_ene...

According to Wikipedia; Calorie:  http://en.wikipedia.org/wiki/Calorie

"The unit calorie has historically been used in two major alternate definitions that differ by a factor of 1000:

    * The small calorie, gram calorie, or calorie (symbol: cal) is the amount of heat (energy) required to raise the temperature of one gram of water by 1 °C.

    * The large calorie, kilogram calorie, kilocalorie (symbol: kcal), or Calorie (capital C) is the amount of heat (energy) needed to increase the temperature of one kg of water by 1 °C, exactly 1000 small calories, or about 4.184 kJ."

According to Wikipedia; Joule:  http://en.wikipedia.org/wiki/Joule

"One joule is the work done, or energy expended, by a force of one newton moving one metre along the direction of the force. This quantity is also denoted as a newton metre with the symbol N·m. Note that torque also has the same units as work, but the quantities are not the same. In elementary units."

According to Wikipedia; Kilowatt-Hour:  http://en.wikipedia.org/wiki/Kilowatt-ho...

"The SI (International System of Units) unit of energy is the joule (J), equal to one watt - second; one kilowatt hour is exactly 3.6 megajoules, which is the amount of energy transferred if work is done at a rate of one thousand watts for one hour."

According to Wikipedia; BTU:  http://en.wikipedia.org/wiki/British_the...

"The British thermal unit (BTU or Btu) is a unit of energy used in the power, steam generation, heating and air conditioning industries. Although it is still used 'unofficially' in metric English-speaking countries (such as Canada, the United Kingdom, and sometimes in New Zealand), its use has declined or has been replaced in other parts of the world. In scientific contexts the BTU has largely been replaced by the SI unit of energy, the joule (J), though it may be used as a measure of agricultural energy production (BTU/kg).

In North America, the term "BTU" is used to describe the heat value (energy content) of fuels, and also to describe the power of heating and cooling systems, such as furnaces, stoves, barbecue grills, and air conditioners. When used as a unit of power, BTU 'per hour' (BTU/h, that is, BTU divided by hour) is understood, though this is often confusingly abbreviated to just "BTU"."