Most misunderstood physics concept

[mfb]

+

Isn't for a photon E=mc²=hf ?
What's wrong with that?

That is correct. But it has nothing to do with mass.

Please start a new thread if you want to discuss this further. Or use the search function, we had many threads about that topic already.

 

[Stavros Kiri]

That is correct. But it has nothing to do with mass.

Please start a new thread if you want to discuss this further. Or use the search function, we had many threads about that topic already.

Thanks. I will look at the threads, time permitted.

 

[papercace]

There is no gravity in space.

 

[jfoldbar]

like i said. i will never "get" it

 

[OmCheeto]

Mass is not a quantum number.

Thank you.
I've been looking for that phrase; "quantum number", apparently, for many years.

Things are starting to make more sense now, and I haven't even started researching this yet.

{edit: I may have just given Tom Mattson the most belated "like" in PF history. [ref] }

 

[davenn]

The one I see over and over again in general physics and EE on here and on many other forums, dozens and dozens of times

" I can't use power supply that can supply more current than what the device is specified for, else the device will burn out "

to which the answer always is ... "No, the device will only draw what it needs (specified requirement)"

then they respond " so what happens to all the other amps ... eg a 1A device on a 10A PSU?"

Answer ... " it doesn't go anywhere, it wasn't there for a start "

Dave

 

[JoePhysics]

The Coriolis force and how some people think it has something to do with the direction in which water swirls as it drains in ordinary-sized objects (bathtubs, toilets, sinks, etc.) on either hemisphere of the planet.

 

[rootone]

like i said. i will never "get" it

A photon has zero REST mass, but a photon cannot be at rest, it is always moving at 'c' for every observer.
This lead to the misunderstanding that photons acquire 'relativistic mass', which idea is now discredited.
However photons still are 'things', and any thing has some momentum. depending on the observer.
For visible light, photons with more momentum are at the blue end of the spectrum, less energetic photons at the red end.

 

[DaveC426913]

Most misunderstood concept?

Science.

And getting worse every day.

 

[Stavros Kiri]

The one I see over and over again in general physics and EE on here and on many other forums, dozens and dozens of times

" I can't use power supply that can supply more current than what the device is specified for, else the device will burn out "

to which the answer always is ... "No, the device will only draw what it needs (specified requirement)"

then they respond " so what happens to all the other amps ... eg a 1A device on a 10A PSU?"

Answer ... " it doesn't go anywhere, it wasn't there for a start "

Dave

They confuse it with voltage. Is that it?
[Voltage and Resistance (or Impedance) give rise to current ... (that means they don't understand Ohm's law properly etc.)]

 

[davenn]

They confuse it with voltage. Is that it?
[Voltage and Resistance (or Impedance) give rise to current ... (that means they don't understand Ohm's law properly etc.)]

no, your second sentence ... a given load resistance will only draw xx amps ... according to Ohms law

 

[Stavros Kiri]

no, your second sentence ... a given load resistance will only draw xx amps ... according to Ohms law

Ok

 

[phinds]

That 'a singularity', such as the one referred to in the case a black hole, is a physical entity with defined properties.

Yeah, that's my candidate as well.

 

[Thecla]

What is the length of a photon? I have heard a wide range of answers .

 

[Richard]

no, your second sentence ... a given load resistance will only draw xx amps ... according to Ohms law

A given resistance will only drop so much voltage based upon the current at that point (E=I*R isn't it?). However total current use as a whole would be computed using Kirchoff's Law. ;)

BTW: What was the big deal with the airplane on the treadmill? If I understood the description right. It had zero net forward motion, therefore no lift. Aerodynamics of air movement above and below the wings makes a plane fly, not engine thrust, or wheel speed. Or am I wrong?

 

[davenn]

A given resistance will only drop so much voltage based upon the current at that point (E=I*R isn't it?). However total current use as a whole would be computed using Kirchoff's Law. ;)

that isn't the problem with the ongoing same question from so many people

they don't understand that a 10A capable PSU ISNT putting out 10A continuously ... rather it only puts out what is drawn by the load

 

[OmCheeto]

...
BTW: What was the big deal with the airplane on the treadmill? If I understood the description right. ...

bolding mine

IMHO, this is why most riddles, especially poorly constrained ones, should NOT be included in "misunderstood physics concepts", as they are open to interpretation.

747 nerds; "If there is a 181 mph headwind, then yes, it will start flying."
Pedants; "Define 'take off'."
Spork and friends; "Well, if you add a propeller to the top, and there's a tailwind...[14 threads and 2 bazillion posts later]...Still not convinced? Here, watch this video."
etc, etc, etc.

ps. I see no one mentioned "temperature" yet:

I guess I still don't understand what "temperature" means...

[edit] Just in case you are interested, and to prevent a thread hijack: Aeroplanes & Conveyor Belts [PF: 2003-2008]

 

[dkotschessaa]

I think hands down the most misunderstood concept is energy. It is used for all manner of whackadoodle new age nonsense.

 

[Nidum]

I'd say that the most misunderstood physics concept of all is just the principle of action and reaction .

 

[nuuskur]

There is no gravity in space.

in tears reading this :D

 

[newjerseyrunner]

Being in space vs being in orbit.

I saw so many people wonder why the guy who BASE jumped from the edge of space didn't burn up in the atmosphere the way the space shuttle does. Seems very few people understand that the shuttle doesn't float in space but has ridiculously high lateral velocity which allows it to fall at the same rate as the curvature.

 

[FactChecker]

Conservation of momentum. When a movie shows a shotgun fired with almost no kick and the person hit gets thrown across the room.

EDIT: I see this is really the same as @Nidum 's post #49.

 

[OmCheeto]

Conservation of momentum. When a movie shows a shotgun fired with almost no kick and the person hit gets thrown across the room.

Fargo, season 2, episode 10, 33:20 from the end.

So glad I wasn't an uber science nerd when I first watched Star Trek TNG.
I recently went back and watched the last three seasons, to see if I had missed an episode, and cringed...

#1; "The anomaly is near the north pole"
Capt; "Very well. Ensign, put us into a synchronous orbit above the north pole"​

And I laughed...

ah hmmm...

Probably not on topic, but that would make a fun thread: "Sciencey things that Hollywoodians get confused with real life":

What's a synchronous orbit?
Probably like synchronized swimming. Things just go round and round.

 

[Farang]

I'm not making fun of the Copenhagen interpretation, I'm making fun of the popularizers who to this day continue to misrepresent quantum mechanics.

What is your take on the subject please? Do you think the many worlds interpretation is correct?

 

[Farang]

Well, since physics is the only real science, evolution must be part of it as well. So yeah, evolution. That makes it what, 44% population of the US and 28% UK(even worse in other places), just don't get it.

 

[XZ923]

IMO the answer to this question can't be anything to do with quantum mechanics or relativity because few people actually pay attention to subjects like that. If we're going for quantity of misunderstanding rather than quality (and yes I do know that understanding or lack thereof cannot be quantified) I think you need something everyone's actively engaged in and most don't understand. Thus it has to be a very basic principle.

I admit I'm biased but IMO the most misunderstood concept has to be the concept of P=VI. Electrical labels are ubiquitous in our society, we all read them, and the lack of understanding of the basic units of wattage, voltage, and amperage is almost as ubiquitous as the labels themselves. Note I did specifically separate it from Ohm's Law because a lot of folks don't do resistance measurements, but everyone's gone to Home Depot or Lowe's thinking "I need a 55W bulb" without any kind of understanding as to what that actually means.

 

[Windadct]

"Not everyone can understand all of physics" : IMO no one can!

People (silly humans) seem very uncomfortable when a concept is beyond their mental grasp, and they then MAKE UP an explanation that suits them, no matter how wrong that may be. The longer the have this explanation in mind and do not learn otherwise, the harder it is for them to accept the accurate theory, or even more difficult to accept that their concept is wrong and they still can not grasp the correct concept. i.e. going from "knowing" to not knowing.

This is why we HAVE TO FIGHT pseudoscience in our schools.

 

[Andy SV]

I used to work with a mechanic who thought making the gear in the back of a bike bigger made you go faster as in top speed faster not merely quicker
I turned him down when he offered to work on my kz650
My cousin swore up and down that the way to make power in a car is to have more vacuum in a carburetor. I was of the opinion that more fuel and air was the trick.

 

[Andy SV]

IMO the answer to this question can't be anything to do with quantum mechanics or relativity because few people actually pay attention to subjects like that. If we're going for quantity of misunderstanding rather than quality (and yes I do know that understanding or lack thereof cannot be quantified) I think you need something everyone's actively engaged in and most don't understand. Thus it has to be a very basic principle.

I admit I'm biased but IMO the most misunderstood concept has to be the concept of P=VI. Electrical labels are ubiquitous in our society, we all read them, and the lack of understanding of the basic units of wattage, voltage, and amperage is almost as ubiquitous as the labels themselves. Note I did specifically separate it from Ohm's Law because a lot of folks don't do resistance measurements, but everyone's gone to Home Depot or Lowe's thinking "I need a 55W bulb" without any kind of understanding as to what that actually means.

I have always thought measuring a light by wattage is silly
When there is a perfectly good lumin

 

[mikeyBoy83]

It is my opinion, as an instructor of physics, that one of the most misunderstood concepts is that of Newtonian dynamics. A lot of people that have a first encounter with physics misunderstand the basic notions of force and as a result motion. This leads to misconceptions in almost any other topic in advanced physics.