Re: [CAD_CAM_EDM_DRO] Re: capacitor

Hi Mariss!

I love word problems... I'll take it on!! I just about have smoke
coming out my ears anyway from running tutorials in half a
dozen cad/cam packages.

Hmm so you burned some gas... you started with a fixed
kinetic energy (1/2mv^2) and ended with the same energy!
So where did that burning gas energy go???

Well I wish you had used an electric car or something.
Since the car is in drive you have the engine running backwards! Practically
such an arrangement cannot be
considered a reversible machine.

But I get the idea. Let's say it is. That means that when
you pump energy into the engine from the drive wheels
of the coasting car going backwards it sucks in exhaust gasses and makes
gasoline which it then pumps in to the tank!
This is then burned when the car goes forward.

That is silly of course... but with true reversible machines
(dc motors and generators) the equivalent would happen!
Lots of electric vehicles work this way-they use regenerative
braking to conserve energy.

OK. The bottom line is that no net energy has been supplied
to the car! And the acceleration? When the car is going
backwards and slowing you will be pressed back in the seat.
As it reaches zero speed you will be pressed back in your
seat. And as it moves faster in the forward direction you
will still be pressed back in your seat.

What you have done is to change linear momentum, which
is a vector.

Newton's law states that the rate of change of linear
momentum of an object is equal to an external force
applied to it.

In other words- F=MA.

OK I had better get back to cam program tutorials...
lest I incur the wrath of an angry list mom.

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.rabun.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.rabun.net/~leswatts/shop.html

----- Original Message -----
From: "mariss92705" <mariss92705@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, March 21, 2002 3:31 PM
Subject: [CAD_CAM_EDM_DRO] Re: capacitor


> Les, Jon,
>
> I don't mean to belabor the point but once I have my teeth into
> something I have to take to its conclusion. That means I have to make
> sure I understand the underlying principle or have others show me
> where I am mistaken.
>
> I am making two assumptions:
>
> (1) "Energy return" during deceleration is not a given.
> (2) There is no difference between acceleration and deceleration.
>
> Both points are tied together in this thought experiment:
>
> Say you are in a car that is rolling backwards at 20 MPH and the
> transmission is in "drive". You apply torque (press the gas) to the
> drive wheels at a constant rate. The car decelerates, stops, then
> accelerates until you are going 20 MPH in the forward direction. Oh
> yeah, and your eyes are closed as well (don't try this at home folks,
> this is a trained professional driver).
>
> The questions are:
>
> (1) If "energy return" is a given, why are you pressing the gas pedal
> during deceleration?
>
> (2) Can you tell when deceleration ends and acceleration begins?
> Remember, your eyes are closed (no peeking).
>
> Mariss
>
>