Will someone settle up on a bet?

[Bruce Tuncks]

My opinion is that OME is wrong about the kilograms but right about the spirit level angle of attack thing. If you are travelling at constant speed at a constant height, then of course the spirit level will tell you the angle of the chord line if it is properly mounted. This angle will increase as you gently slow down. Until you stall.

Whether or not this is a useful instrument in the real world is another matter. On my Jabiru, the stall warning horn thingy is an amazingly long way towards the underside of the leading edge, and the whole plane is correspondingly very nose up at the stall. I have never heard it sound on landing, and indeed the tail skid/fin would prevent the stall angle of attack unless the mains were about a metre above the ground. On a normal landing, the mains are closer to the ground but I don't feel the tail hit first. Should I? 

Anyway, I enjoy reading the stuff OME comes up with and I hope he continues.

 

[facthunter]

I'll make a command decision, here.   The topic WAS re-opened. and Peter made a worthy contribution.. One comment. The depth of the presentation should be relevant to  it's application to flying or many will not bother to put in the effort  to engage in a very academic and complex approach to basic physics..  A s for stating your credentials who would know if you were telling the truth?  The "quality and clarity" of your presentation and particularly it's usefulness as you perceive it, count. You have to "sell" your line not impose it. Nev

Edited April 6, 2021 by facthunter

[old man emu]

1 hour ago, facthunter said:

A s for stating your credentials who would know if you were telling the truth?

True.

I suppose that one's credibility to others depends on the reputation one has earned. By that, I mean that I hope that when the topic is of a serious nature, my reputation is that what I say has merit. On the other hand, I am quite happy to have the reputation for quick wit and repartee in the appropriate place. That means my reputation is like two-sided Roman god Janus

Peter clearly identified that I often use the Socratic method to "sell" my line. I suppose that in these busy modern times, people don't want to lounge under an olive tree and philosophise over a flagon of Chian wine (the most prized wines in classical Greek antiquity). People want the sound grab. So one must try to suit the "market". As for those who are  happy to engage in a very academic and complex approach to basic physics, rebuttal must be at the same level of complexity as the proposition.

 

My biggest annoyance with the "weight/mass" thing is that no one was prepared to accept that the two words refer to different things. The words arise from different concepts

 

weight (n.): Old English gewiht "weighing, weight, downward force of a body, heaviness," from Proto-Germanic wihti-. The original sense of the Old English verb wegan  "find the weight of, measure; have weight; lift, carry, support, sustain, bear; move, was of motion, which led to that of lifting, then to that of "measure the weight of." The older sense of "lift, carry" survives in the nautical phrase weigh anchor.

 

mass (n.): late 14c., "irregular shaped lump; body of unshaped, coherent matter," from Old French masse "lump, heap, pile; crowd, large amount; ingot, bar" (11c.), and directly from Latin massa "kneaded dough, lump, that which adheres together like dough," probably from Greek maza "barley cake, lump, mass, ball," which is related to massein "to knead," from PIE root *mag- "to knead, fashion, fit."

[Jabiru7252]

I think this topic should be taken behind the tractor shed at lunch time and sorted out there.

 

[old man emu]

I asked Ian to close the original thread. 

 

Do you think that if a few of you asked for this thread to be closed, that he would? I think it should as it's going nowhere.

[facthunter]

It's, OK to close it. Betting shouldn't be encouraged. One vote from me. BUT IF it relates to the original thread title who wants limited knowledge of Lift and stuff. It's the essence of heavier than air flight.  Nev

[facthunter]

OME in what manner do your definitions of MASS  (above) support the scientific concept of it.? Common usage by the person in the street is generally quoted by modern dictionaries.. You don't say the weight of a plane has increased in a banked turn but IF you are aware the loads are increased by what "G" they are affected by  including the normal earth's 1 G it's capable of being. analysed and understood by all.. These conversations often degenerate into semantics rather than understanding. Nev

[Peter Piper]

I did not say that OME used a socratic method. No one was using socratic questining. Socratic questioning would be a way forward.

[Thruster88]

How do we ask if a litre of water has a mass of 100 grams in Socratic?

[aro]

6 hours ago, old man emu said:

My biggest annoyance with the "weight/mass" thing is that no one was prepared to accept that the two words refer to different things. The words arise from different concepts

 

I don't think anyone is arguing with the idea that they refer to different things - rather that it's so obvious it goes without saying.

 

The argument is whether something with a mass of 1 kg weighs anything other than 1 kg, when "weigh" is used in it's everyday usage i.e. stationary on the surface of the earth, ignoring local variations in gravitational force, and using kg to refer to kg-weight.

 

From Wikipedia:

The kilogram was originally defined in 1795 as the mass of one litre of water. This was a simple definition, but difficult to use in practice. By the latest definitions of the unit, however, this relationship still has an accuracy of 30 ppm.

 

i.e. the difference between the mass of 1 litre of water and the current SI definition of a kg which uses the Planck constant is less than 0.003%. For our purposes, the mass of 1 litre of water is close enough and much simpler to understand.

 

If you take 1 litre of water, which has a mass of 0.999972 kg using the SI definition and put it on your scales, it is going to read 1 kg within the limits of accuracy of any regular set of scales.

 

All this reference to the Planck constant, Avogadro's number etc. is just obfuscation - it is not necessary for discussion of the topic.

 

Edited April 6, 2021 by aro

[old man emu]

It seems the experts (physicists) can't even come up an all inclusive definition of "mass". From https://physics.stackexchange.com/questions/192564/why-is-the-definition-of-mass-and-matter-interlinked

 

About the proper definitions, mass actually has three, but these are not very proper too:
The inertial mass of an object is its resistance against acceleration by force.
The gravitational mass of an object is the object's tendency to be attracted by a gravitational field.
The relativistic mass is the mass of the total energy stored in a system, where mass is simply defined by the relation E=mc^2 to be a physical quantity directly proportional to energy, by a factor of c^2=89875517873681760m^2 s^-2

 

It would appear that when "weigh" something, you are noting its gravitational mass, which is where the F = ma comes in, and your answer is in newtons. When you try to move an object, you are dealing with inertial mass, which is also F = ma, but in this case "a" is not the acceleration due to gravity, 9.81 m/s^-2. It is something less. That's clear if you want to push a car along a flat road. You only have to overcome the friction in the wheel bearings and the tyre contact patch, which is usually taken to be about 0.01 x 9.81 etc. or less in total.

 

The relativistic mass is related to the number of particles (atoms) you have in your lump of matter. Those atoms have the energy, so you can work out the mass if you know the energy released by its fission. Efficiently burning 2100 litres of petrol would produce the same amount of energy as fission of 1 gram of uranium, so I guess this method of determining mass is more theoretical than practical.

 

 

[Bruce Tuncks]

I thought Einstein was impressed by the fact that inertia and gravity cannot be separated out. Thus was born the idea of space-time and that gravity was the effect of warping space-time.

If this were not so, you could imagine an instrument which was a perfect artificial horizon.

BUT what about the Higgs boson, I wonder...  " the particle which bestows mass".   In my poor understanding, this runs counter to the space time stuff.

[facthunter]

The question is not in the  BAK exam.  Nev. 

[Admin]

Thread closed