Energy Storage Model - Unit Summary

Energy Storage Model

Unit Summary

The Energy Storage Model is used to observe how energy is used and transferred. Energy is a conserved, substance-like quantity with the capability to produce change. It does not come in different kinds but, rather, different forms. 

Eg - Gravitational Energy

Eel/Esp - Elastic Energy/Spring Energy

Echem - Chemical Energy

Ek - Kinetic Energy

Etherm - Thermal/Heat Energy

Ediss - Dissapated Energy

To represent the transfer of energy in a graph, we use pie charts and LOL charts. 

Pie charts are qualitative representations of the energy in a system. The size of the each piece of the pie chart indicates how the energy is distributed throughout the event. The size of the circle itself represents the total energy of the system. 

For example, if an object rests on a coiled spring and, then, is launched upwards, you can represent the event with three pie chats.

For an LOL chart, you can use energy bar graphs to display a quantitative analysis of the event. The initial energy is represented with a bar graph showing the amount of energy stored in the beginning of the event. Then, in the middle, a circular flow chart indicates which items are inside and outside the system. The last bar graph represents the energy transfer at the end of the event. By using the information from the bar graphs, you can come up with a mathematical expression to represent the event. 

For example, if a moving cart travels 5.0 m/s collides with a spring, you can use an LOL chart to discover the maximum compression of the spring. 

If you choose to exclude the spring from the system, the chart will look a lot different. An outside force would be called a work force.

Hooke's Law

Concentrating on Eel, you can find the Eel stored in a spring with Hooke's Law. 

Eel = 1/2KX^2

The spring constant can be found when observing a graph measuring force vs. displacement. The rise/run equals the spring constant. N/M can also give you the spring constant because rise/run is, on a graph, measuring the N and M. 

Other important equations are:

Ek = 1/2mv^2 to find the kinetic energy 

Eg = mgh to find the gravitational energy 

Eth = FfrX to find the thermal energy 

W = Fx to find the work force when a force is acting outside the system 

P = Etrans/t to find the amount of energetic power

J/S = Watts

Power is different than energy. In terms of calories, Power is what calories are converted into in order for you to be active. It can be found by, first, determining the Ek in an event. 

For example, if someone eats a 700-calorie lunch and radiates about 100 J per second, you can determine how long it will take them to radiate away their lunch with the Power equation. 

If 1 food calorie = 4186 J, then the person transferred 2,930,200 J of energy. Dividing this by 100 (J/s) will give you the amount of time it will take to radiate away the lunch. 29, 302 seconds or 8 hours.

By using the graphical representations as well as the equations, you can solve numerous word-problems and physics situations to find the values of different energies.