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| 183_notes:energy_cons [2021/05/25 15:52] – [Defining systems] stumptyl | 183_notes:energy_cons [2021/05/25 15:53] (current) – [Multi-particle Systems] stumptyl |
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| ==== The Total Energy of a System Can Change ==== | ==== The Total Energy of a System Can Change ==== |
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| [{{ 183_notes:conservation_of_energy.001.png?300|When work is done //by// the surroundings on the system, the total energy of the system increases. Energy from the surroundings is being "dumped" into the system.}}] | [{{ 183_notes:system_work_7.png?300|When work is done //by// the surroundings on the system, the total energy of the system increases. Energy from the surroundings is being "dumped" into the system.}}] |
| [{{ 183_notes:conservation_of_energy.002.png?300|When the system does work //on// the surroundings, the total system energy decreases. Energy from the system is being extracted.}}] | [{{ 183_notes:system_work_7.1.png?300|When the system does work //on// the surroundings, the total system energy decreases. Energy from the system is being extracted.}}] |
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| __**We observe that the total change in energy of a system and the system surroundings is zero.**__ This means that whatever energy change we observe in the system, is exactly taken up by the surroundings. That is, if the system energy goes down, then the energy of the surroundings must go up. | __**We observe that the total change in energy of a system and the system surroundings is zero.**__ This means that whatever energy change we observe in the system, is exactly taken up by the surroundings. That is, if the system energy goes down, then the energy of the surroundings must go up. |
| ==== Multi-particle Systems ==== | ==== Multi-particle Systems ==== |
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| [{{ 183_notes:system_puzzle.png?400|Two cases of a ball falling from rest with different choices of system.}}] | [{{ 183_notes:earth_7.png?400|Two cases of a ball falling from rest with different choices of system.}}] |
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| Consider a ball initially at rest that begins to fall towards the Earth. | Consider a ball initially at rest that begins to fall towards the Earth. |