Recent content by Doug1943

But "air pressure is due to the weight of the air above" is the way it is explained in almost every popular science book, and on the first dozen or so web links you get if you Google the phrase. Your definition would confuse beginners. We want to teach kids how to think ... not to memorize...

Yes. That's why I said, "Now reduce the height of the cylinder (of air) from 100 km, to 5 meters. And close the top of the cylinder as well. Make the cylinder very very strong, and 'airtight'. Lift this closed cylinder up a few kilometers above the Earth's surface. The air pressure outside the...

You didn't understand the original statement. The argument is not "Air pressure doesn't exist". Rather, the argument is: it is misleading to talk of the 'weight of the air above' as the cause of this pressure, as if we had a pile of bricks above. But taking your example (which I reproduce for...

Yes. It's sloppy to talk of pressure as a force when in fact it's the ratio of force to the area to which the force is applied. That settled, what do you think about the argument that saying air pressure is due to the 'weight of the air above' is misleading?

I've read lots of physics books. You don't know what you're talking about, unfortunately -- you're one of the types of student that Feynman was talking about: satisfied with some memorized words that will get you the "correct answer" on the exam, and uninterested in actually understanding reality.

All the popular definitions of 'air pressure' that I have seen say: "air pressure is the weight of the column of air above you". This seems misleading to me. - -...

is there some physical limit on the wavelength of electromagnetic radiation? Can there be radiation shorter than gamma rays?

Oh well ... the thought was meant kindly. In fact, they ought to run all of these science lessons, especially the online ones that young people are likely to encounter, and on their own, past a group of physicists before sending them out into the world. In principle, things like Bitesize are...

That's very interesting. .. I looked at the other threads related to Newton's First Law, and saw this discussed ... but didn't feel I understood the whole idea of an 'inertial reference frame'. Have to dig deeper.

Ah ... nice idea. I wonder if there is a YouTube video of something like that? I know that the three Laws are interlinked ... some people like to see Number 1 as a special case of Number 2 ... and in both cases, we are neglecting Number 3 at first. And of course the relativeness of motion --...

Yes, that sounds like an interesting way to address this issue. What I was really trying to get at was this: everyone experiences the world. Everyone knows that 'things fall down' (and not up) ... except when they float ... and that heavier things fall faster than lighter ones. They know...

Yes, agreed.

Here's an example of what I mean: "A force causes an object to undergo a specific change. Unbalanced forces cause changes in speed, shape or direction" ... [ From: https://www.bbc.com/bitesize/guides/zyydmp3/revision/2 ] I've seen this reference to 'shape' several times. [I live in the UK and am...

I think it's nothing as grand as that, unfortunately. And yes, it's a real problem. Kids are all too willing to accept any old improbable crazy or outright meaningless idea you tell them, if it's with the authority of The Teacher. They don't expect it to apply to the real world -- school-facts...

Of course not. Let's extend the image: two cannon balls floating in zero g, connected by a loose chain. I poke one ... what happens? Or, a long steel bar. I give a push to one end. What happens? Before we can try to analyze such situations, we need to abstract away from these complexities...