[[Work Energy and Power]]

Power is how fast energy moves or changes form.

# Summary
* SI Unit is Watts (W), where 1 W = 1J/s
* Average power is energy change over time: $P_{avg}=\frac{\Delta E}{\Delta t}$. Work changes energy so $P_{avg}=\frac{W}{\Delta t}$
* Instantaneous power for a constant force: $P_{inst}=F_{||}v=Fv\cos \theta$ using only force component parallel to velocity.
* Sign of power tells direction, positive means energy added negative means energy removed.
* When an object moves at a constant speed, energy is zero.

# Average Power Calculation
$$P_{avg}=\frac{\Delta E}{\Delta t}$$
Examples:
* 60 watt light bulb transfers 60 joules into light and heat.
* 1500 watt hair drier running for 5 minutes transfers 1500 * 300 watts.
* Solar panel generating 500 watts per second stores 500 joules to be used later.

# Power as Work Rate
$$P_{avg}=\frac{W}{\Delta t}$$
Power can be calculated by dividing work by time taken.

# Instantaneous Force from Power
$$P_{inst}=F_{||}v=Fv\cos \theta$$