obsidianvault/physics/Work Energy and Power/Power.md

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