Car accelerators (off topic)

[L Nyveen <lawrence@dsuper.net>]

At 13:47 -0500 18/12/98, Thomas R. Holtz, Jr. wrote:

>You hold a car's accelerator constant
>to keep a constant speed.

That's actually correct terminology.

Force = mass x acceleration, right?

Well, on a car, like a plane, you four main forces: lift, gravity, drag,
and thrust.

Lift and gravity (with the help of the suspension) can be ignored.  So all
you have is thrust and drag.

Assume a car in a vaccuum - with on board oxygen.  :)  Let's ignore
friction for now.  If you depress the accelerator, say, 2 inches, it will
accelerate forever, continuously increasing speed (let's also ignore
relativity).

If you depress the accelerator 4 inches, it will accelerate faster.

In real life, you have drag to balance thrust and drag increases with
speed.  If you depress the accelerator 2 inches, the car will accelerate
until it reaches a speed at which thrust=drag.  If you depress it 4 inches,
it will do the same, but the final speed will be higher than at 2 inches.

We now return you to All My Turtles.


Laurie Nyveen                                  lawrence@dsuper.net
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