Energy Use

One of the Special Topics the students are preparing for next week is about energy use. We talked about Newton's Law, F=ma, and how one can change that way of describing motion to, mv^2/2 + mgh = constant, then and there energy appeared in the high school classroom. Somehow though, I felt I was not getting across. Do the students know that when they go to the gas station, they are paying for energy?

After several days we went in a field trip to Six Flags, Great America, on Physics Days. Again; what is kinetic energy, and potential, and mechanical energy? Do they relate that to the price of gasoline?

I do not feel that most of us internalize what we learn at school and real life.

Some tips to understand, why gasoline is over three dollars a gallon?

"PROVIDENCE, R.I. (AP) -- If you've stopped to fill up your tank recently you've seen it: Gas prices have surpassed the three-dollar mark.

The state Energy Office says its latest survey found gas averaging three dollars and one cent a gallon. That's seven cents more than last week. It's also an increase of 82 cents, or 37 percent over this time last year.

A survey by Triple-A of Southern New England finds gas prices averaging three dollars a gallon."

Let me start with F=ma. I know my students ask me not to derive equations, just tell us what the equations are, and how to use them.

I feel that if I use words and no equations, I am allowed to "derive" results.

Newton wrote over three hundred years ago that inertia requires an external agent to change velocity. Let's see; car is at rest in the garage, or wherever you parked it. Inertia being what it is, it won't budge. It weighs over a few thousand pounds. We have two options, we may pull it with a rope, there is the F of old Isaac, or just turn on the motor. Little electric spark, and the fire inside starts. Somehow we don't see the force now, but the internal combustion engine is on fire, and it moves the wheels.

Where did that fire inside the gasoline come from?

To the best of my knowledge, there were dinosaurs happily munching food sixty five million years ago in the Yucatan peninsula; a big rock hit the Earth, and they passed away. After many years they became oil, and then gasoline.

First tip.

Rocks like that, do not come often; that is our good luck. Many of them and we will go the way of the dinosaurs.

Scarcity means high prices. That is the first tip to explain three dollars a gallon.

Second tip.

The Yucatan dinosaurs are being sold now by Mexicans and Americans, there are Arabs selling theirs also. Dead dinosaurs are a non-renewable resources.

Third tip.

We should be getting the energy from where the dinosaurs got it. Frist from plants, and then from the Sun directly.

How does F relate to energy?

That is called the work-energy theorem, that will be a different post on this site.