The misery of school

[sicetaitsimple]

The fly, since it remains at a constant altitude, transfers its weight to the ground by accelerating packets of air (air molecules) which collide with it and tend to push it back (increase in pressure) with a distributed force equal to his weight.

Nonsense... If it remains at a constant altitude, its weight is compensated by an "upward" force (lift), a "suction", which compensates for it. And so this weight applies more on the scales.
But OK..
With such false reasoning, if they are spread by teachers, it's true that it can't really help the school....

[izentrop]

The fly, since it remains at a constant altitude, transfers its weight to the ground by accelerating packets of air (air molecules) which collide with it and tend to push it back (increase in pressure) with a distributed force equal to his weight.

Nonsense... If it remains at a constant altitude, its weight is compensated by an "upward" force (lift), a "suction", which compensates for it. And so this weight applies more on the scales.
But OK..
With such false reasonings, if they are spread by teachers, it's true that it can't really help the school....[/quote]
Certainly not. A physics teacher who released this enormity would not have had his diploma. The student would have had a zero.

[Exnihiloest]

...
With such false reasoning, if they are spread by teachers, it's true that it can't really help the school....

Certainly not. A physics teacher who released this enormity would not have had his diploma. The student would have had a zero.

...
Nonsense... If it remains at a constant altitude, its weight is compensated by an "upward" force (lift), a "suction", which compensates for it. And so this weight applies more on the scales.
...

Fake. Upward force equals weight, ok, but like any mechanical force, upward force requires a "fulcrum". This fulcrum is the air, which redispatches the force on the earth. The plane leans on the air, thanks to the lift, the air leans on the ground, so we find its weight at the bottom (but not just below or instantly, of course).
When I put my ice cube in the whiskey (because I'm only offered a low-end blended), the glass weighs more than the weight of the ice cube, while the ice cube floats, its weight also being balanced.

You guys disappoint me, you're going to have to revise, Falcon is right.

[fracass]

Anyone to set up an experiment? A precise scale, a transparent box, and a fly... With the cold it will be hard to find a fly that flies...

Why will the air necessarily be on the bottom of the box? The successions of pressure/depression are carried over the entire surface of the box, right?

[Exnihiloest]

Who would think that this gadget would only weigh the weight of the stand?!

The force F balances P but P ends up exerting a downward tension on the wire, which is transferred to the rod of the support. The rod carries the weight of the plane. With a real airplane, the stem is the air.

avion.png (572.75 KiB) Viewed 1129 times

[izentrop]

Anyone to set up an experiment? A precise scale, a transparent box, and a fly... With the cold it will be hard to find a fly that flies...

A small drone that is stable in hovering flight can do the trick

Why will the air necessarily be on the bottom of the box? The successions of pressure/depression are carried over the entire surface of the box, right?

If the fly flies at least 2 times the width of its wings or 2 times the width of the rotor for a helicopter, it is obvious that there is no influence on the balance, except turbulences of a swirling air on himself.

Your stiff iron rod can't fake an Exni dynamic air.
https://www.lavionnaire.fr/HelicoMecaVol.php

[Remundo]

Izy reasons about both COVID and physics. Digression, paralogism, figure of speech.

to sum up: to compensate for its weight, the plane (or the fly!) leans on the air and the air in turn leans on the ground.

It's relentless, and it ain't even mechanics fluids. It's Newton's 3rd law...

This is the principle of reciprocal actions.

[SebastianL]

The archaeologists of the future will have fun with this topic.
What is ground effect? just a local increase in pressure, out of hydrostatic equilibrium.
A glass of water + ice cube is in hydrostatic equilibrium.

Lift is the ratio of average intrados/extrados pressure x the surface, well the ground increases the intrados pressure.
The air, it doesn't have musky little arms to make a chain from the wing to the ground. On the other hand, when air is projected onto the ground, the local pressure increases, out of hydrostatic equilibrium.

It's quite amazing to come and support a theory, which had already led you to defeat with your "diode wind generator".

[Remundo]

the ground effect in effect is an additional force when the aircraft flies very close to the ground.

it concerns airplanes and also helicopters or other jet engines with downward nozzles.
* in the case of airplanes, the proximity of the ground increases the volume under pressure near the wings (in front of the intrados)
* in the case of downward blowers when the airflow hits the ground and is deflected at 90°: if we make a balance of momentum on this deflected air, this creates a thrust greater than that which it would be when the fluid simply flows downward unhindered.

the 2 phenomena can be combined.

But we don't need these aero tricks to understand that in all cases, the support force of the plane on the air is also that of the air on the ground.

[SebastianL]

But we don't need these aero tricks to understand that in all cases, the support force of the plane on the air is also that of the air on the ground.

No and no. All of this is a popularization, and a bad one because it's wrong about basic physics.
Already we speak of "force" as if we were in static, first error, the plane has a lift in return for a drag x the speed of the wing = the engine power.

All the experimenters have observed that the ground effect makes it possible to have the same lift at reduced power, thus reducing overall drag.
A little more pressure on the intrados
A little less depression on the extrados
But above all high and low pressures closer to the hydrostatic pressure of the atmosphere = less turbulence by shearing, lower intrados - extrados speed delta = less drag.
The aircraft attitude is flatter at ground level