Wednesday, April 2, 2008

Obey the LAW!

Hi Mick:

First I want to apologize for taking up some of your time, I know how extremely busy you are. The reason I am writing to you is that all my life I keep coming up with ideas and I do not know where to bring them. When I though of my latest one you came to mind. This has probably been thought of a thousand times but you don’t know until you mention it. I has to do with the electric car. My idea is to have a fifth wheel connected to the car underneath the trunk whose sole purpose is to generate electricity while the care is in motion. It would be hinged in a fashion that it would bounce along with the bumps in the road. It would omit a constant current to the engine when moving at speeds over 10 mph, then switch over to the batteries to store energy for starting up again when you come to a complete stop. Dumb huh?

My other idea is, do you remember the hood scoops on the muscle cars? Why can’t you put a small wind turbine in there to generate electricity also.

Thanks for listening! Don’t be too hard on me…….


I won’t be too hard on you. But you do need to study and apply the laws of physics. Bear with me and I’ll explain.

The First Law of Thermodynamics says that energy is neither created nor destroyed, only transferred from one form to another. The Second Law says that no energy transfer is 100% efficient.

The First Law tells us that if a car is moving along the road using a battery or other engine to make the movement happen, then we are transferring energy from chemical storage to kinetic (motion) energy. The Second Law says that these transfers will always be somewhat inefficient, and we will lose energy as heat and friction, primarily to the air, and to the tries. Tires are always warmer after a trip. If you don’t believe me, feel to be sure. So the chemical energy of the fuel or the battery is no made into motion, then through friction that becomes heat in the tire. If you have breakfast, and then digest your breakfast, and a few hours rub your hands together until they’re warm, where does the energy in those hot hands come from?

So we add either a fifth wheel or a wind turbine to this system. But the energy we use to drive the system down the road in the first place comes from the battery or engine. We are not adding new energy. So any energy generated from the fifth wheel or the turbine comes from where?

It turns out it comes from the chemical energy in the battery or the vehicle fuel, just like your hot hands are from the energy in your breakfast. And because no energy transfer is 100% efficient, we actually don’t use some portion of the energy for vehicle motion. It’s just wasted.

Having said that, hybrids like the Prius use generators in each wheel to charge the battery on down hills and braking. In a sense this is free braking that doesn’t wear out brake pads and also helps move the car forward. More efficient.

So not so dumb after all....

Here endeth today’s lesson about the Law (of physics)


1 comment:

CoolClay said...

Well put, I have had to explain very similar vehicle physics issues with people before, and it ain't the easiest thing in the world.