Work Energy Theorem
Read the introduction to work and energy then answer the following questions on the Student Worksheet.
| Student Worksheet PDF |
Energy
An object which possesses energy is able to do work. In fact, energy is often defined as the ability to do work. Any object which possesses energy - whether it be in the form of potential energy or kinetic energy - is able to do work. That is, its energy enables that object to apply a force to another object in order to cause it to be displaced.
Potential Energy
An object can store energy as the result of its position. For example, the heavy ram of a pile driver is storing energy when it is held at an elevated position. This stored energy of position is referred to as potential energy. Anything that can fall has gravitational potential energy. A stretched rubber band has tensional potential energy. Potential energy is the stored energy of position possessed by an object.
Kinetic Energy
Objects also store energy in motion. A moving mass can certainly exert forces, as you would quickly observe if someone ran into you in the hall. Energy of motion is called kinetic energy. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy.
Conservation of Energy
Energy is never created or destroyed; energy only gets converted from one form to another. This concept is called the law of conservation of energy. The rule we found for the input and output work of a machine was an example of the law of conservation of energy.
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In these animations you can see the total mechanical energy never changes,
but the energy gets converted back and forth between potential and kinetic energy. As the height increases so does the potential energy. As the speed increases so does the kinetic energy. The total energy never changes. |
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Work
Work is the conversion of one form of energy to another. For mechanical systems it is a force applied over a distance.
Examples of work converting energy: Your push a car up a hill. Your chemical potential energy in your muscles is being converted to kinetic energy (motion) and gravitational potential energy (height)
When gravity pulls the car down the hill (doing work) it is converting the potential energy you gave the car into kinetic energy by making the car speed up.
Examples of work converting energy: Your push a car up a hill. Your chemical potential energy in your muscles is being converted to kinetic energy (motion) and gravitational potential energy (height)
When gravity pulls the car down the hill (doing work) it is converting the potential energy you gave the car into kinetic energy by making the car speed up.
Concept Check:
1. Write a brief summary of this information. Be sure to include potential energy, kinetic energy, work, and conservation of energy as well as explaining how they are all related.
