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### Power & Simple Machines

• Power is a measure of how quickly we put work into a system. Mathematically,
 P = W t .
• Since work is a transfer of energy (W=∆E), we can also formulate power as
 P = ∆E t .
• Finally, we can also formulate it as
 P = → F · → v
[Note: this requires you to use the dot product for vectors. If you aren't familiar with dot products, this is equivalent: P = |F| |v| cosθ.]
• Power has the unit of joule per second ([J/S]). We call this a watt (W).
• Simple machines are based on the idea of conservation of energy. Instead of using a large force over a small distance, we can use a small force over a large distance and still put in an equivalent amount of work.

## Power & Simple Machines

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