Energy
Here is the Unit Outline.
What is energy? The ability to do work, that means applying a force to move sometime a certain distance. We will talk about this more later. For now, here are some examples of different types of energy.
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| Kinetic Energy: the energy of moving things. |
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| Sound Energy: energy from sound waves. |
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| Electric Energy: energy from moving charges. |
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| Thermal Energy: the energy from heat. |
Energy can be stored in one form or another called Potential Energy.
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| Elastic/Spring potential energy. |
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| Chemical Potential Energy in batteries. |
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| Chemical Potential Energy in foods. |
Energy can also be stored in fields.
- Gravitational Potential Energy: the energy stored in gravitational field.
- Electric Potential Energy: the energy stored in electric fields.
The most important types we will talk about are Kinetic and Gravitational Potential Energy. We will also discuss thermal energy towards the last half of the unit.
The most important thing you can understand about energy is the following:
- ** Energy cannot be created or destroyed. **
- ** Energy can only change from one form to another. **
Energy and Society
Since we can’t create energy, so we have to harness it from somewhere…
- The sun —> Solar Energy
- From atoms —> Nuclear Energy*
- From the Earth —> Geothermal Energy
- From wind —> Wind Energy
- From water —> Hydroelectric*
- Oil, Coal, Natural gas —> Fossil fuels
* are the two main forms of energy in Ontario.
This device converts kinetic energy into electrical energy to charge your phone.
Definition: energy is the ability to do work. Work is defined as a force acting over a distance.
W = F∆d
- ** Work is NOT a vector.
- ** F and ∆d must be in the same direction, multiply the magnitudes.
- ** Any force can do work.
What are the units of work?
Looking at the formula…
[Units of work] --> N•m = (kg•m/s²)•m = kg•m²/s² = J
J stands for Joules and is a shortcut for writing kg•m²/s²
James Joules showed that mechanical energy can convert to heat.
He used this brilliant device to measure the falling of a mass and the temperature rise of water inside a sealed container.
Homework
Read P. 165-167,Do practice problems P. 167 #1,2,3
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