Impact is the Key

[Fletcher]

On the other hand a fuel burning helicopter hovering in one place is not doing any work either but it sure is expending energy.

But work is being done Ralph - if you take the newtonian view of action & reaction the rotary wing of the helicopter is pushing a mass of air downwards - this mass of air reacts with the surrounding molecules in a chain fashion setting up an equal & opposite reaction force allowing the helicopter to hover - no burning fuel, no rotating wing, no hover, & the helicopter was doing work on the air mass - you just have to change the perspective to see who or what is doing the work !

If however you take the view that the helicopter hovers due to Bernoulli's theorem then the Newtonian view is displaced & the angle of attack creates some air mass movement downward but the opposite lifting force is due to low air pressure topside of the rotating wing - since the force beneath is greater than that above there is unequal forces & the unequal force topside is exactly equal to the force exerted by gravity, allowing the helicopter to hover - work was still being done, no fuel burn, no rotating wing, no hover.

[ovyyus]

We agreed earlier about dropping a magnet down a conductive tube. It does not fall at a natural rate building in velocity. Would you agree that the magnet must be doing work resisting gravity?

No. The effort of lifting the magnet against the force of gravity to the top of the tube provides the magnet with the potential to heat (do work on) the tube as it falls. What resists gravity?

Now we are discussing the terminology of the word 'work' which I see no point in.

I agree, let's stick with the physics definition of 'work'. Do you agree with the standard definition of 'work'?

I think Fletcher covered the helicopter question well, ie: a hovering helicopter burns lots of fuel doing lots of work constantly accelerating a mass of air downwards in order to create a reaction force equal and opposite to the force of gravity. Can you give a better example of something that might be expending energy without doing any work?

[Michael]

Bill,

You know I am always up and ready for a debate on a down to earth topic.

As for testing the strength (or fragility) of what we hold to be true is right up my alley! Providing the topic is worthy or related to hands on research and not an on going debate about protons, photons and how fast is the speed of gravity compared to light.

IMO gravity is an attraction force not unlike a magnet, the attraction force is governed by the size and density of the mass attracting it. Earth is the mass and 32 feet per second 2 is the attractive force of the planet we live on. Saturn, Jupiter and Mars all have varying rate of gravitational velocity.

As for a aspirated combustion engine; without gravity there would be no intake stroke.

Ralph

It's weak Ralph ( and a little mean spirited ) for you to beef yourself up by putting down other topic threads that you feel you might either be unqualified or uninterested in contributing to.

I also believe your triad logic at times to be too simplistic and somewhat Aristotlian;

"In places, Aristotle goes too far in deriving 'laws of the universe' from simple observation and over-stretched reason."

[greendoor]

A suction plunger sticking to a wall ... held there by air pressure. Is work being done? Is energy being expended? I expect we would all say No work, No energy expenditure.

But what would happen if all energy left the room? The air molecules would be at Absolute Zero. Would they still apply force to the suction plunger? Isn't it fair to say that every air molecule is in constant motion, and without that there could be no air pressure? At some basic level, is work not being done, and energy not being used?

I don't know - I hate gettting bogged down in academic semantic time wasting. I'm just a basic mechanic that wants to build practical devices.

For example: if you want to get really academic about stuff, it's impossible to measure the perimeter of a circle, or a countries coast line. Because the finer the unit of measure you choose to use, the greater the perimeter or boundry gets. You have to trace out every minute detail of the boundry - which gets increasing more complex. But to arrive at the most accurate answer, you have to go to smaller & smaller units. Down to the particle level, I suppose - at which point you would give up and say it is impossible to measure the perimeter of anything. Or you could just say it's infinite, because the most accurate unit of measure is infinitely small ...

Anyway - my point is too much book learning does yer head in ...

[Fletcher]

Anyway - my point is too much book learning does yer head in ...

LOL, so true - & another to ponder.

"Learn from others mistakes, there are far to many for you to make in your lifetime !"

[rlortie]

Bill wrote;

I agree, let's stick with the physics definition of 'work'. Do you agree with the standard definition of 'work'?

Here is a brevity edited context of my compiled definition of work, thanks to two encyclopedias and one engineering hand book.

Work, in physics, product of a force applied to a body and the displacement of the body in the direction of the applied force. While work is done on a body, there is a transfer of energy to the body, and so work can be said to be energy in transit. That is; The transfer of energy or mass from one place or system to another. The units of work are identical to those of energy. If, for example, an object is lifted from the floor to the top of a table, work is done in overcoming the downward force of gravity, and the energy imparted to the body as work will increase its potential energy. That potential energy is also doing work when the book is allowed to fall. Work is also expended when a force accelerates a body, such as the acceleration of off the book falling from the table back to the floor.

The force need not be simply a mechanical force as in the case of lifting a body or accelerating a plane by jet reaction; it can also be an electrostatic, electrodynamic, or surface-tension force (see Electricity; Surface Tension).

On the other hand, if a constantly acting force does not produce motion, no work is performed. Holding a book steadily at arm's length, for example, does not involve any work, irrespective of the apparent effort required. Nor does the helicopter, just as we burn calories holding the book creating heat the helicopter burns combustible fuel. When hovering stationary it is no different than holding a book or a magnet on the refrigerator.

To clarify farther, yes I agree that the helicopter blades are doing 'work' as a mass is moving, but the mass or embodiment of the helicopter is not.

In the commonly used English system of units, the unit of work is the foot-pound (ft-lb), which is equal to the amount of work required to raise a mass of 1 lb through an elevation of 1 ft at sea level and 45° latitude. In the CGS system, a force of 1 dyne moving through 1 cm corresponds to 1 erg of work. The more commonly used practical unit of work or energy in the CGS system is the joule, which equals 107 ergs. The rate of doing work is known as the power. The application of 550 ft-lb/sec, for example, corresponds to 1 horsepower, abbreviated hp, in the English system.

This is what I accept as standard definition of 'work'.

Will you agree that a falling accelerating mass using gravity as its potential source of energy is doing 'work'? Mass is being transmitted from one place to another!

Ralph

[graham]

Will you agree that a falling accelerating mass using gravity as its potential source of energy is doing 'work'? Mass is being transmitted from one place to another!

Thinking about it I would have to say no.

I would say yes if you were asking if work were being done if a mass were being raised against the force of gravity.

Graham

[rlortie]

Graham,

Why do you say that a book or any falling mass which is being displaced does not fit the basic terminology of the word 'work'?

I reiterate;

Work, in physics, product of a force applied to a body and the displacement of the body in the direction of the applied force.

We have an applied force (gravity) displacing a (falling) body in the direction of the applied force; any falling object is doing work. If it falls fast enough and far enough it will create heat, a byproduct of work.

I would say yes if you were asking if work were being done if a mass were being raised against the force of gravity.

Is it not falling against the force of wind resistance?

With gravity or without gravity the same mass is being displaced. 'Work' does not include the resistance of any force applied to the mass moving from point A to B, only the distance moved defines 'work' in the examples used here.

This is the kind of debating that I see no useful purpose in when it comes to researching for Bessler's secret. We know the damn book is going to fall if given the opportunity. In a gravity wheel, what difference will arguing over nomenclature solve?

Ralph

[graham]

Absolutely none Ralph.

Just for informations sake I quote the following:

A Force does no work unless the system is free to move "along the direction" of the Force applied. When a Force and the object's displacement are perpendicular, the work done by the force is zero.

The meaning here is not clear to me , how about you?

I read this here
http://www.ac.wwu.edu/~vawter/PhysicsNe ... nWork.html

Graham

[Fletcher]

Here I go oversimplifying again but maybe this will clear things up for some, in a practical application sense, perhaps, & from a laymans view.

A force is an agent of change - it causes a body to move [have motion] - that body will accelerate having new velocity & Kinetic Energy of motion, determined by that velocity - the force is the 'Prime Mover', the body acted on & now in a changed state of motion the Secondary player in the system, having gained kinetic energy as a result of the force acting on it.

If two body's interact [after at least one has been acted on by a force] then provided that there is still movement together or away from each other [a distance gradient] the system still has capacity to do & is still doing work - if both body's remain together after contact so that the distance between them is unchanged [i.e. relative motion is ceased] then work is no longer being done with regards to their localised subset system, as there is no longer any kinetic energy gradient or distance gradient between them.

e.g. a fridge magnet once attached to the fridge cannot close the distance any further [zero distance gradient] so no work is being done in the system after contact [N.B. the Prime Mover force (magnetism) is still acting] - the helicopter blades are constantly moving a mass of air downwards while hovering so at least one part of the system is still in motion relative to the other, therefore at least one constituent part of the system has mass in motion [distance & Ke gradient still in evidence] & therefore work is still being done.

That may or may not be useful Ralph but it is how I visualize work in mechanical macro systems to mean.

[ovyyus]

Holding a book steadily at arm's length, for example, does not involve any work, irrespective of the apparent effort required...

Incorrect. There's lot's of work going on inside the body such as muscle twitching, heating, etc. I didn't think that was any great mystery???

...When hovering stationary it is no different than holding a book or a magnet on the refrigerator.

Also incorrect. As already said, we observe the helicopter doing lot's of work pushing around lot's of mass (air). On the other hand the magnet isn't doing any work for precisely the same reason.

Will you agree that a falling accelerating mass using gravity as its potential source of energy is doing 'work'? Mass is being transmitted from one place to another!

Yes, of course. Ralph, it surprises me that you persist with an argument based on such arbitrary imposed limits. Doesn't it seem incomplete to apply this limited view to falling books when you already know that books don't just fall from nowhere? You seem reluctant to consider the full account.

Talking to a windmill operator about the physical properties of wind would probably seem pointless to him - he doesn't need to know the relationship between pressure and heat in gas in order to mill wheat. So then what does one talk to a windmill operator about, besides the milling and the weather?

[rlortie]

A copy and paste from Grahams above link;

The Force does the Work, not the agent that created the Force. Do not confuse the work you do to create a force with the work done by the force you create; they are not the same. The force you exert holding a 100 pound barbell above your head does no work on the barbell while the barbell is at rest, but you do work (on a molecular level) to create that force.

Barbell, book or helicopter, no work is done if the mass is stationary and that is my point.

Ralph wrote:
Holding a book steadily at arm's length, for example, does not involve any work, irrespective of the apparent effort required...

Incorrect. There's lot's of work going on inside the body such as muscle twitching, heating, etc. I didn't think that was any great mystery???

There is a lot of work going on inside the body just as their is in the helicopter blades but no work is done if the mass is stationary.

Yes, of course. Ralph, it surprises me that you persist with an argument based on such arbitrary imposed limits.

It surprises me even more, all we are doing is debating the terminology of the word 'work'. If I lift a book from point A to point B and drop it, you will say no work was done as I had to create a force Resistance to gravity. You cannot seem to except the fact that yes work was done lifting the book from A to B and gravity supplied the force to move it from B to A. Work was accomplished in both direction using force.

Then some one will say that no work was done as the book has returned to its original position. I say work was done by gravity going from B to A.

Doesn't it seem incomplete to apply this limited view to falling books when you already know that books don't just fall from nowhere? You seem reluctant to consider the full account.

True books do not fall from just anywhere. I do consider the full account. Work was performed to get the book anywhere and gravity performed work returning it. Energy was spent and the fact remains work was done.

And by the way with this view in mind the helicopter blades did not do work as the air returned to its ambient state.

Talking to a windmill operator about the physical properties of wind would probably seem pointless to him - he doesn't need to know the relationship between pressure and heat in gas in order to mill wheat. So then what does one talk to a windmill operator about, besides the milling and the weather?

Truer words were never spoken, he has wheat to mill and I for one have wheel designs to physically research. Talk to me about gravity wheels, not the meanings of a four letter word called 'work'.

Graham if you deem that gravity is not a force capable of performing work and when a mass is retained by another force such as a person, no work is accomplished on the mass. Then what are your muscles retaining that Fletcher says is work?

Please do not misunderstand me as Fletcher is correct, he simply is not looking at the subject from my point of view. If it takes work to hold up a book in a non-working status then their must be an opposing force, it is called gravity.



Enough! I have wheat to grind and a lawn to mow! No more 'armchair philosophy' for a while please. I do not need to hear that mowing my lawn is not work as will grow back. All in jest please! :-)


Ralph

[docfeelsgood]

if that chopper hovering is doing no work then why not replace the engine with a hand crank . i think ya better consume about 10 kilos of aunt jemima flapjacts in case it does turn out to be work afterall . imoo .

[greendoor]

If a tree falls in a forest, and gazillion other trees each clap one hand, would Ovyyus hear anything? Discuss.

[ovyyus]

It surprises me even more, all we are doing is debating the terminology of the word 'work'.

But we already agreed on the standard definition of work - there is no debate on the terminology.

No more 'armchair philosophy' for a while please.

Armchair philosophy? I thought we were debating observable and down to earth physical processes???