Everyday Physics: Estimating Values for Energy
We live in a world of energy. You store energy in your body by eating food. Your car transforms the energy in gasoline into motion. Even your phone has a battery that stores energy. But what about the actual numbers? How can we compare the numerical values for energy in different cases? Let’s go over some of my favorite calculations.
What is a Joule?
There are many different units for energy, but the best is the Joule. There’s no question about this — the Joule is the one you should use. In terms of fundamental units, we have the following:
But still, that’s just a number. Here’s an example that can help you relate to the numerical values. Take a textbook and put it on the floor. Now lift the textbook up and put it on a table. It would look like this.
The textbook will probably have a mass somewhere around 1 kilogram and the table is probably about 1 meter above the ground. Since the gravitational field is 9.8 Newtons per kilogram, this gives a total work of something on the order of 10 Joules. Lifting the book required you to use 10 Joules of energy. There — now you know about Joules.
