OT: LOTD and a Q for the brainiacs

Turn off your computer and start reading, ya lazy bum!

But why is that not "force?" Voltage is called "electromotive force," even when there's no current flow. I'm just simply confused by the daffynition above, "In physics, a force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape." which sounds like you're saying that if there's no movement, no force is involved.

Did I get a bum steer on what "force" actually is, or what?

Thanks, Rich

Hey, I'm reading right now, albeit most USENET posts are a far cry from Asimovian. ;-)

Cheers! Rich

Indubitably, my dear Po. I'm actually spending the day in bed (mostly) and reading W.E.B. Griffin's _The Hostages_. Next in the stack are the CNC book by Alan Overby and the SketchUP (missing) manual.

-- Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive. -- Howard Thurman

Because it's a "reaction". YOU made it the reaction by defining the hand as the force.

Voltage is called "electromotive force,"

Force equals mass times acceleration. Mass by itself is not a force and acceleration by itself is not a force. Combine mass and acceleration and you get force. Your hand moving in space will attempt to accelerate (change the velocity of) anything it comes in contact with. A scalar is a defined distance, velocity is the rate of change of a scalar with respect to time and acceleration is the rate of change of velocity with respect to time. Say a car moves one mile, that's a scalar. The car moves one mile at constant speed in a certain time, that's velocity. The car moves one mile starting from a full stop and gets up to speed at one mile, that's acceleration. Confusing? The wall won't move even though you are pushing on it, you're trying to accelerate the wall even though it won't move, don't matter. phil

"Phil Kangas" wrote in message news:ihst29$6os$ snipped-for-privacy@news.eternal-september.org...

I like this better than OT stuff so I'm going to add:

Force cannot exist by itself, it is the result of the interaction of two entities that can exist each on their own and you have control of. Think of this example. You're gonna pound that nail into that block of wood. Under what circumstance can you apply force to drive it in? You only know the size of the nail and the weight of the hammer you're going to use. How hard do you swing the hammer, easy? Light? You'll only know when you hit the nail, if you can. Any misses won't apply the needed force. When you do hit it on the head the mass of the nail and the acceleration of the hammer create the force you need, and that force immediately disappears when the nail stops. Make sense? phil ;>))

I've had to write a newsgroup filter for you as a direct result of your two most recent posts, Phil.

But that is *good* because your name will now be highlighted in my reader to show that you are among a select few individuals that will receive my careful attention because of the stellar quality of your posts.

Thank you!

--Winston

The spring did change shape when elastically loaded or deflected enough to make it push or pull with 1 lb of force.

Force.

Force.

Forces can (and usually do) exist in static situations where nothing is moving.

That's the source of considerable confusion. One definition of acceleration is dV/dt, time rate of change of velocity. If velocity is changing, motion is indeed a requirement.

But then, to explain a force proportional to mass as in F=M*a, Newton decided that gravity is an acceleration even where there is no motion or rate of change of velocity. But the units work out right so gravity is an acceleration in that form of definition, even though there is no dV/dt.

Well, this still doesn't answer my question, but it does bring to mind that elevator car they use for Einstein's postulate of equivalence - you can't tell from inside the car if you're sitting at 1G or if you're flying through space...

But if you were being swing around in a centrifuge with a radius of

But if you hang a weight from a fish scale, what's it measuring, if not "the force of gravity?" (note "force" here.)

In fact, in one of my brother's physics books, there were two pictures - one of some guy pushing on a wall, captioned "Force with no motion," and the other a diagram of a planet in orbit captioned "Motion with no force." The point of the article was that in either case there was no _work_ being done.

But I'm still dogging that thing that for there to be "force," there has to be movement of some kind.

Or has that been answered, I didn't notice, and I'm off in the wild blue yonder?

Thanks, Rich

so, once the shape is done changing there, is there still "force?"

And yo've finally given me the answer I wanted to hear. ;-)

Thanks! Rich

The Force is weak with this one...

Find an anvil, or perhaps a grand piano. Place anvil or one leg of grand piano on testicles.

After squashing motion has ceased, is there still force?

Of course, but it's at the atomic level...

You're welcome! You made my day! ;>)) phil