Everyday Einstein explores how work, energy, and power are related.
A long time ago when I was much younger, I worked with my father in his landscaping business, which consisted primarily of cutting the grass at gas stations. Now, you might not think that gas stations have much grass, but I can tell you that some of them would surprise you. But no matter how much grass a gas station had, I earned a steady stream of $5 per gas station.
Unfortunately for me, while it took quite a long time to earn that money, I spent it at a much faster rate. This was mainly because I was an avid comic-book reader and all of the gas stations that needed their grass cut also sold comic books. (It was diabolical!)
In my mind, cutting grass, earning money, and buying comic books will forever be connected. Such is the relationship between work, energy, and power..
Energy, the Currency of Work
If you remember our discussion about potential and kinetic energy, you know something about energy already, such as the fact that energy can’t be created or destroyed, only converted from one form to another. One of my favorite physics websites is Georgia State University’s Hyperphysics site. On that site they call energy the “currency” for performing work.
When I was cutting grass for my father, I was storing up currency, which in my mind was the capacity to buy comic books. The value of comic books I could purchase was equal to the amount of currency that I had stored up through cutting grass.
Similarly, the amount of work you can do is equal to the amount of energy you have available. Just like I was paid in the same currency that I needed to buy comic books (U.S. dollars), energy and work are measured using the same quantity, joules. If I wanted to buy $5 worth of comics, I had to do $5 worth of grass cutting. If you want to perform 100 joules of work, you need 100 joules of energy.