25 lines
1010 B
Markdown
25 lines
1010 B
Markdown
[[Work Energy and Power]]
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Power is how fast energy moves or changes form.
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# Summary
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* SI Unit is Watts (W), where 1 W = 1J/s
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* Average power is energy change over time: $P_{avg}=\frac{\Delta E}{\Delta t}$. Work changes energy so $P_{avg}=\frac{W}{\Delta t}$
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* Instantaneous power for a constant force: $P_{inst}=F_{||}v=Fv\cos \theta$ using only force component parallel to velocity.
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* Sign of power tells direction, positive means energy added negative means energy removed.
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* When an object moves at a constant speed, energy is zero.
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# Average Power Calculation
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$$P_{avg}=\frac{\Delta E}{\Delta t}$$
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Examples:
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* 60 watt light bulb transfers 60 joules into light and heat.
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* 1500 watt hair drier running for 5 minutes transfers 1500 * 300 watts.
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* Solar panel generating 500 watts per second stores 500 joules to be used later.
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# Power as Work Rate
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$$P_{avg}=\frac{W}{\Delta t}$$
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Power can be calculated by dividing work by time taken.
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# Instantaneous Force from Power
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$$P_{inst}=F_{||}v=Fv\cos \theta$$
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