Intro to Physics.

Everskyward said:
I took a introductory course in Physics in HS and another one in college. I think they helped me understand some flying concepts although that is not why I took the courses. That's not to say that I would recommend taking a Physics class since most of the concepts are simple and logical even without any background. I'm also not sure what help it would be after the fact.
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I took five physics classes in college. After Newtonian motion stuff I would never use the words simple and logical to describe the classes. We did a lot of work with Einsteinian near relativistic speed work with both the special theory and then general theory of relativity. Then a whole lot of quantum work where not a whole lot made any sense at all!!! GAWD! It made me hate all the work I was doing in semiconductor design at the time. That engineering class was about how to make a diode, transistor, etc. and you applied a lot of the theory about particles that one was learning in physics. But those classes where way beyond the intro type classes that most people took.

One question on a test we had was a lot of fun. You may remember the old joke, if you are traveling at the speed of light in a car and turn on your head lights what would happen? Well that was a test question in one of my classes and you needed to show mathematically why your answer was correct.

ANSWER:
I don't have the math handy, but the answer was you would slow down to a sub light velocity
 
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ScottM said:
I took five physics classes in college. After Newtonian motion stuff I would never use the words simple and logical to describe the classes.
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I was only using "simple and logical" to describe the physics which are helpful in understanding flying an airplane. I don't mean designing an airplane either, just the basics of vectors, velocity, forces, acceleration, mass and the different forms of energy. There's no way I would call the extensive study of physics "simple". In fact I never got that far.
 
ScottM said:
ANSWER:
I don't have the math handy, but the answer was you would slow down to a sub light velocity
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I'm not sure this makes sense. You are using a violation of the law to illustrate the law.
 
jasc15 said:
I'm not sure this makes sense. You are using a violation of the law to illustrate the law.
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It was a college test question, not an illustration that I made up. I cannot remember if he said the car was massless or maybe just a fraction under c as the speed. The prof had a whole bunch of conditions as part of the question. But I figured the audience here was not going to actually try the derivation of the question and I cannot remember all of it anyways. I do remember my grade though. 14/100 points and that was the 2nd highest score in the class. Thank FSM for the curve!
 
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ScottM said:
It was a college test question, not an illustration that I made up. I cannot remember if he said the car was massless or maybe just a fraction under c as the speed. The prof had a whole bunch of conditions as part of the question. But I figured the audience here was not going to actually try the derivation of the question and I cannot remember all of it anyways. I do remember my grade though. 14/100 points and that was the 2nd highest score in the class. Thank FSM for the curve!
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And my students think MY tests are hard!!

Seriously though, I agree with Joe that the question doesn't seem to make sense. If the car was massless it wouldn't have headlights to turn on. (I mean, what is it made of, neutrinos?) And if you were traveling near c in whatever vehicle and turned on your headlights, it would be no big deal to you. A stationary observer would see the light just barely inching away from you, but to you, it would be a normal light beam, traveling at speed c. Something's fishy. :dunno:
 
azure said:
And my students think MY tests are hard!!

Seriously though, I agree with Joe that the question doesn't seem to make sense. If the car was massless it wouldn't have headlights to turn on. (I mean, what is it made of, neutrinos?) And if you were traveling near c in whatever vehicle and turned on your headlights, it would be no big deal to you. A stationary observer would see the light just barely inching away from you, but to you, it would be a normal light beam, traveling at speed c. Something's fishy. :dunno:
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Define "stationary".
 
All knowledge helps your understanding of the Universe.. Does physics help, yes. But aerodynamics is the most important thing to understand. And more important than that is when the airplane goes nose left correct with right rudder. That said, pilots with a better undersanding of the physics/aerodynamics of flight seem to progress much faster. I try to incoroporate as much as I know [marginal] about the aerodynamics to help the students who don't know understand the WHY so they don't go testing other theories [as much].. Still it usually amounts to, more lift on the "up" wing, more induced drag, adverse yaw, compensate with rudder. Which is about the limit of my understanding and I am a CFI for better or worse. How does the wingtip vortice [if that is the cause] actually increase induced drag? IDK and even if I did I would [probably] overload the student I am trying to teach a simple task like flying coordinated.

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azure said:
And my students think MY tests are hard!!

Seriously though, I agree with Joe that the question doesn't seem to make sense. If the car was massless it wouldn't have headlights to turn on. (I mean, what is it made of, neutrinos?) And if you were traveling near c in whatever vehicle and turned on your headlights, it would be no big deal to you. A stationary observer would see the light just barely inching away from you, but to you, it would be a normal light beam, traveling at speed c. Something's fishy. :dunno:
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That's precisely what would happen. That's because your concept of time (travelling near c) would be so greatly slowed that what appeared to the outside observer as inching ahead of you would appear to you to be racing away at c.

The invariant nature of c is the whole purpose behind concepts like time dilation within special relativity.
 
JeffDG said:
That's precisely what would happen. That's because your concept of time (travelling near c) would be so greatly slowed that what appeared to the outside observer as inching ahead of you would appear to you to be racing away at c.

The invariant nature of c is the whole purpose behind concepts like time dilation within special relativity.
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And that may be showing some cracks...some constants might not be constant across the universe

http://prl.aps.org/abstract/PRL/v107/i19/e191101

for a simpler explanation:
http://www.laboratoryequipment.com/...cy-of-Physics-May-Not-Be-Constant-110311.aspx
 
I have been always puzzled by the inertia effects of where a force is not felt unless there is a change in the velocity (acceleration) vector. Unlike a liquid or a gas medium where the force (drag) is felt at a constant velocity. What kind of medium (space) will only be sensitive to a change in velocity. The property of inertia is a must to maintain order in the universe but how the fabric of space accomplish this is what has been puzzling me since my college days. Neither Einstein or Newton never address the how is done. Any Einstein wanna be here has some idea about the subject.

José
 
Ill second the multiple universes theory. (just cause it sounds cooler)

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You can't fix stupid.

Dan Thomas said:
A pilot doesn't need to know the complexities of physics but he sure should have a grip on the basics. Too many have killed themselves when they did a low-and-over and pulled up sharply (or did some other load factor-increasing maneuver) and stalled and spun the airplane just because they didn't understand that published stall speed relates only to the 1G condition. Too much of PPL groundschooling is rote stuff that doesn't sink in.

Dan
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This is not a book, but a link to a series of short video explaniations of the concepts. There is a whole series of things, based on about a high school level. They cover lots of topics in math and science.

http://www.khanacademy.org/#physics
 
JeffDG said:
That's precisely what would happen. That's because your concept of time (travelling near c) would be so greatly slowed that what appeared to the outside observer as inching ahead of you would appear to you to be racing away at c.
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Exactly. I meant (hopefully this was clear) that there was something fishy about the premise of the question posed by Scott's professor. There is nothing special about moving close to the speed of light except that it gets harder and harder to go faster (again, from the "stationary" observer's perspective) because you have more and more inertia. Small increments of speed correspond to huge increments of kinetic energy.

Actually, now I'm wondering if he wasn't saying that light from headlights moving close to c would carry so much momentum that the reaction force would slow the car down significantly. I don't think that's correct, but I haven't really thought about it.
 
Erice said:
This is not a book, but a link to a series of short video explaniations of the concepts. There is a whole series of things, based on about a high school level. They cover lots of topics in math and science.

http://www.khanacademy.org/#physics
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One of my students told me about that site. From what I have seen it is a nice resource for students and even teachers. I go there occasionally looking for better ways to explain difficult concepts. But it's really a supplement rather than a complete course in basic physics.
 
azure said:
Exactly. I meant (hopefully this was clear) that there was something fishy about the premise of the question posed by Scott's professor. There is nothing special about moving close to the speed of light except that it gets harder and harder to go faster (again, from the "stationary" observer's perspective) because you have more and more inertia. Small increments of speed correspond to huge increments of kinetic energy.

Actually, now I'm wondering if he wasn't saying that light from headlights moving close to c would carry so much momentum that the reaction force would slow the car down significantly. I don't think that's correct, but I haven't really thought about it.
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The other thing that was neglected from the scenario is that you can't "turn on" something when travelling at c. Time is stopped for massless particles at c. It's part of the proof that neutrinos have some mass is that they experience oscillation between electron neutrinos, muon neutrinos and tau neutrinos showed that they could not be travelling at c.
 
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JeffDG said:
The other thing that was neglected from the scenario is that you can't "turn on" something when travelling at c. Time is stopped for massless particles at c. It's part of the proof that neutrinos have some mass is that they experience oscillation between electron neutrinos, muon neutrinos and tau neutrinos showed that they could not be travelling at c.
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The propagation of light is actually a wave in the space medium much like sound in air. This is why its constant velocity does not change with the velocity of the source. The appearance of time dilation is due to the slow down of the aging process within the vehicle. Changes in the atomic structure (aging) are determined by the relative velocity. This is analog to trying to speak to the pilot in front of an open cockpit plane at the speed of sound, it will never hear you because the sound wave will never arrive. If your speed is slightly lower it may take several seconds to reach the front pilot. If aging was affected by the speed of the conversation between the two pilots you could see how travelling close to C will cause an appearance of time dilation.

The fact that the speed of light is unaffected by its source proves that it propagates through a medium in space very much like sound in air. The characteristics of this medium is what controls all physical events.

José
 
Capt. Geoffrey Thorpe said:
Physics for the sake of Physics or Physics as related to aerodynamics?

"Introduction to Flight" but John D. Anderson, Jr.

Covers the fundamentals of aerospace engineering. Surprisingly light on the calculus and is quite readable. The current edition goes for text book prices, but I was able to pick up an older edition (third) for about $20. Well worth it.
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If this is the book I'm thinking of it has a few chapters of really good history then gets straight into some pretty hairy equations.

Doc
 
MBDiagMan said:
If this is the book I'm thinking of it has a few chapters of really good history then gets straight into some pretty hairy equations.

Doc
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Define "hairy"

It had some pretty basic calculus - but it's hard to get around that.

He also has an "Introduction to Aerodynamics" that I have not read. Perhaps that had more math?
 
Piloto said:
The fact that the speed of light is unaffected by its source proves that it propagates through a medium in space very much like sound in air. The characteristics of this medium is what controls all physical events.

José
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That sounds an awful lot like luminiferous aether, a theory that has been disproven by a number of experiments. Light does not travel through a medium.
 
JeffDG said:
That sounds an awful lot like luminiferous aether, a theory that has been disproven by a number of experiments. Light does not travel through a medium.
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Yeah, we weren't allowed to graduate with a degree in Physics unless we could explain the concept of the aether and how it was disproven. It was a pretty dang simple experiment.
 
Piloto said:
The fact that the speed of light is unaffected by its source proves that it propagates through a medium in space very much like sound in air. The characteristics of this medium is what controls all physical events.

José
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Those theories have been well disproven:
http://en.wikipedia.org/wiki/Aether_theories

by these guys:
http://en.wikipedia.org/wiki/Michelson-Morley_experiment

Any physicist worth their salt can tell you off the top of their head how that experiment was done. Even better is that the physicist should have done the experiment as part of their undergraduate study.
 
COFlyBoy said:
Those theories have been well disproven:
http://en.wikipedia.org/wiki/Aether_theories

by these guys:
http://en.wikipedia.org/wiki/Michelson-Morley_experiment

Any physicist worth their salt can tell you off the top of their head how that experiment was done. Even better is that the physicist should have done the experiment as part of their undergraduate study.
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Notice that I never refer to aether but "space medium". And even the above mentioned experiments do not totaly disqualify the aether concept. Recent research has proven that there is no empty space. Otherwise how would you explain the constant velocity of light or the inertia effects.

José
 
Capt. Geoffrey Thorpe said:
Define "hairy"

It had some pretty basic calculus - but it's hard to get around that.

He also has an "Introduction to Aerodynamics" that I have not read. Perhaps that had more math?
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I'll try to remember to check the book when I get home to see if this is it.

If it IS the same book, I would think the equations would be hairy for someone entering College Physics 101.
 
Piloto said:
Notice that I never refer to aether but "space medium". And even the above mentioned experiments do not totaly disqualify the aether concept. Recent research has proven that there is no empty space. Otherwise how would you explain the constant velocity of light or the inertia effects.

José
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If you have a medium, then the speed of light would not be the same in different reference frames, it would be constant with respect to the medium. That would mean that if you're driving in a car at c-1 m/s and you flipped on your lights, you would see the light creep ahead of you at 1 m/s. A medium creates an "absolute" reference frame that is completely inconsistent with relativity.
 
Piloto said:
Notice that I never refer to aether but "space medium". And even the above mentioned experiments do not totaly disqualify the aether concept. Recent research has proven that there is no empty space. Otherwise how would you explain the constant velocity of light or the inertia effects.

José
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I'd love to see that! Please post.
 
JeffDG said:
If you have a medium, then the speed of light would not be the same in different reference frames, it would be constant with respect to the medium. That would mean that if you're driving in a car at c-1 m/s and you flipped on your lights, you would see the light creep ahead of you at 1 m/s. A medium creates an "absolute" reference frame that is completely inconsistent with relativity.
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Unless you are in a nested medium universe.

A fish underwater will have a hard time observing the inertia effects upon itself because the water medium in which it lives will override (drag) the inertia effects that are visible in empty space. Like the fish it is conceivable that we exist in a universe of nested mediums. This may explain the orthogonality of some effects between electromagnetics and mechanics.

José
 
Piloto said:
Unless you are in a nested medium universe.

A fish underwater will have a hard time observing the inertia effects upon itself because the water medium in which it lives will override (drag) the inertia effects that are visible in empty space. Like the fish it is conceivable that we exist in a universe of nested mediums. This may explain the orthogonality of some effects between electromagnetics and mechanics.

José
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Sounds like the stuff posted on news groups.
 
So suppose the cosmic speed limit is only true for light and a neutrino COULD go FTL.. If it's mass is 0 at C and time NULL and all that jazz does an FTL neutrino's mass have to be multiplied by i?

<---<^>--->
 
p1l0t said:
So suppose the cosmic speed limit is only true for light and a neutrino COULD go FTL.. If it's mass is 0 at C and time NULL and all that jazz does an FTL neutrino's mass have to be multiplied by i?

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Yes...the equations of special relativity dictate that if a particle's velocity is > c, then it's mass must be imaginary.
 
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