britincali wrote:If you fire a bullet in a plane towards the front of a plane traveling at say 1400 mph (rough guess on a bullett???) the bullett would be going 2800 mph.
Now if you fire it towards the rear it may fall out of the barrell.
So, using that obviously bong derived logic, if the plane can fly faster than the bullet and "you fire it towards the rear," the bullet will not only not "fall out of the barrel," but actually get pushed back into the shell casing?! Like the gunpowder isn't going to build any pressure in the barrel just because it's moving?
I don't care how fast that plane is traveling or from whatever frame of reference you look at it, that bullet is gonna exit the barrel.
Haha, and you talk shit about the American education system.
Inside the barrel you have pressure forcing it to accelerate out.
Im talking about when it exits the barrel from an exterior gun.
I should have made that clearer As I already posted inside the plane everyone and everything is doing the same speed aside from the bullett which is obviously going faster relative to everyone inside.
Lets just say if a bullets speed exiting the barrel is 1000 mph (rearwards) and a plane is doing 1000 mph (forwards) the bullet will drop like a stone.
Like I said before inside as in the interior of the plane is a different matter.
Say a plane is travelling at 1000 mph forward and fire a bullet towards the rear at 1000 mph, the bullet IS doin 0 mph (relative to ground speed) but the speed of the plane will still make it hit whatever at 1000mph.
If you switched ends and fired foreward the bullet IS doing 2000 mph (relative to ground speed) but is still doing 1000mph relative to the planes speed.
Last edited by britincali on April 17th, 2010, 11:49 pm, edited 9 times in total.
Coolness list by 90cr500guy
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OK, there is a plane traveling in one direction at 1000 mph. A tail gunner in that plane fires a gun with a muzzle velocity of 1000 mph in the opposite direction of the planes travel.
The tail gunner will “see” the bullet move away from him at 1000 mph.
An observer on the ground will “see” the plane move away from the bullet at 1000 mph.
Neither of those observers will “see” the bullet “fall out of the barrel.”
"Last edited by britincali on Sat Apr 17, 2010 10:49 pm; edited 9 times in total" <--- That's gotta be some kind of record!
Does the photon have mass? After all, it has energy and energy is equivalent to mass.
Photons are traditionally said to be massless. This is a figure of speech that physicists use to describe something about how a photon's particle-like properties are described by the language of special relativity.
The logic can be constructed in many ways, and the following is one such. Take an isolated system (called a "particle") and accelerate it to some velocity v (a vector). Newton defined the "momentum" p of this particle (also a vector), such that p behaves in a simple way when the particle is accelerated, or when it's involved in a collision. For this simple behaviour to hold, it turns out that p must be proportional to v. The proportionality constant is called the particle's "mass" m, so that p = mv.
In special relativity, it turns out that we are still able to define a particle's momentum p such that it behaves in well-defined ways that are an extension of the newtonian case. Although p and v still point in the same direction, it turns out that they are no longer proportional; the best we can do is relate them via the particle's "relativistic mass" mrel. Thus
p = mrelv .
When the particle is at rest, its relativistic mass has a minimum value called the "rest mass" mrest. The rest mass is always the same for the same type of particle. For example, all protons, electrons, and neutrons have the same rest mass; it's something that can be looked up in a table. As the particle is accelerated to ever higher speeds, its relativistic mass increases without limit.
It also turns out that in special relativity, we are able to define the concept of "energy" E, such that E has simple and well-defined properties just like those it has in newtonian mechanics. When a particle has been accelerated so that it has some momentum p (the length of the vector p) and relativistic mass mrel, then its energy E turns out to be given by
E = mrelc2 , and also E2 = p2c2 + m2restc4 . (1)
There are two interesting cases of this last equation:
1. If the particle is at rest, then p = 0, and E = mrestc2.
2. If we set the rest mass equal to zero (regardless of whether or not that's a reasonable thing to do), then E = pc.
In classical electromagnetic theory, light turns out to have energy E and momentum p, and these happen to be related by E = pc. Quantum mechanics introduces the idea that light can be viewed as a collection of "particles": photons. Even though these photons cannot be brought to rest, and so the idea of rest mass doesn't really apply to them, we can certainly bring these "particles" of light into the fold of equation (1) by just considering them to have no rest mass. That way, equation (1) gives the correct expression for light, E = pc, and no harm has been done. Equation (1) is now able to be applied to particles of matter and "particles" of light. It can now be used as a fully general equation, and that makes it very useful.
Is there any experimental evidence that the photon has zero rest mass?
Alternative theories of the photon include a term that behaves like a mass, and this gives rise to the very advanced idea of a "massive photon". If the rest mass of the photon were non-zero, the theory of quantum electrodynamics would be "in trouble" primarily through loss of gauge invariance, which would make it non-renormalisable; also, charge conservation would no longer be absolutely guaranteed, as it is if photons have zero rest mass. But regardless of what any theory might predict, it is still necessary to check this prediction by doing an experiment.
It is almost certainly impossible to do any experiment that would establish the photon rest mass to be exactly zero. The best we can hope to do is place limits on it. A non-zero rest mass would introduce a small damping factor in the inverse square Coulomb law of electrostatic forces. That means the electrostatic force would be weaker over very large distances.
Likewise, the behavior of static magnetic fields would be modified. An upper limit to the photon mass can be inferred through satellite measurements of planetary magnetic fields. The Charge Composition Explorer spacecraft was used to derive an upper limit of 6 × 10-16 eV with high certainty. This was slightly improved in 1998 by Roderic Lakes in a laboratory experiment that looked for anomalous forces on a Cavendish balance. The new limit is 7 × 10-17 eV. Studies of galactic magnetic fields suggest a much better limit of less than 3 × 10-27 eV, but there is some doubt about the validity of this method.
Speed of light
From Wikipedia, the free encyclopedia
Jump to: navigation, search
"Light barrier" redirects here. For the device, see Photoelectric sensor.
For other uses, see Speed of light (disambiguation) and Lightspeed (disambiguation).
The Earth orbits the Sun at a distance of 150 million kilometers, and the Moon in turn orbits the Earth.
Sunlight takes about 8 minutes, 19 seconds to reach Earth.
Speed of light in different units metres per second 299,792,458
kilometres per second 299,792.458
kilometres per hour 1,079 million
miles per second 186,282.4
miles per hour 671 million
astronomical units per day 173
Planck units 1 (exact)
Travel times at the speed of light Distance Time
one foot 1.0 ns
one metre 3.3 ns
one kilometre 3.3 μs
one statute mile 5.4 μs
from the geostationary orbit to Earth 119 ms
the length of Earth's equator 134 ms
from Moon to Earth 1.3 s
from Sun to Earth (1 AU) 8.3 min
one parsec 3.26 years
from Alpha Centauri to Earth 4.4 years
across the Milky Way 100,000 years
from Andromeda Galaxy to Earth 2.5 million years
All values are approximate unless noted otherwise.
The speed of light (usually denoted c) is a physical constant. It is the speed at which electromagnetic radiation (such as light) travels in vacuum, the speed of massless particles, the speed of a null path in relativity, and the fastest speed at which energy or information can travel. Its value is exactly 299,792,458 metres per second,[1][2] often approximated as 300,000 kilometres per second or 186,000 miles per second (see the table on the right for more units).
For much of human history, it was not known whether light was transmitted instantaneously or merely very quickly. In the 17th century, Ole Rømer first demonstrated that it traveled at a finite speed by studying the apparent motion of Jupiter's moon Io. After centuries of increasingly precise measurements, in 1975 the speed of light was known to be 299,792,458 m/s with a relative measurement uncertainty of 4 parts per billion. In 1983, the meter was redefined in the International System of Units (SI) as the distance traveled by light in vacuum in 1⁄299,792,458 of a second. As a result, the numerical value of c in meters per second is now fixed exactly by the definition of the meter.[1][2]
According to the theory of special relativity, c connects space and time in the unified structure of space time, and its square is the constant of proportionality between mass and energy (E = mc2).[3] In any inertial frame of reference, independently of the relative velocity of the emitter and the observer, c is the speed of all mass-less particles and associated fields, including all electromagnetic radiation in free space,[4] and it is believed to be the speed of gravity and of gravitational waves.[5][6] It is an upper bound on the speed at which energy, matter, and information can travel,[7][8] as surpassing it "would lead to the destruction of the essential relation between cause and effect."[9] Its finite value is a limiting factor in the operational speed of electronic devices.[10]
The speed at which light propagates through transparent materials, such as glass or air, is less than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c / v). For example, for visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s; the refractive index of air for visible light is about 1.0003, so the speed of light in air is very close to c.
Redrocket, I’m sure those are good google answers but hells bells, just too long to be reading on a bike forum, I was thinking more about the discovery channel type answers.
"Last edited by britincali on Sat Apr 17, 2010 10:49 pm; edited 9 times in total" <--- That's gotta be some kind of record!
Because you pissed me off and the first 4 were nasty then the last 5 were edits to make sure I spelled shit rite and wouldnt have your bitchass quoting me on fukups
Coolness list by 90cr500guy
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
"Last edited by britincali on Sat Apr 17, 2010 10:49 pm; edited 9 times in total" <--- That's gotta be some kind of record!
Because you pissed me off and the first 4 were nasty then the last 5 were edits to make sure I spelled shit rite and wouldnt have your bitchass quoting me on fukups
ellett wrote:OK, there is a plane traveling in one direction at 1000 mph. A tail gunner in that plane fires a gun with a muzzle velocity of 1000 mph in the opposite direction of the planes travel.
The tail gunner will “see” the bullet move away from him at 1000 mph.
An observer on the ground will “see” the plane move away from the bullet at 1000 mph.
Neither of those observers will “see” the bullet “fall out of the barrel.”
:
Yes and no....
The tail gunner would see the bullets drop the second they came out of the barrel, yes he would see them move away at 1000mph but they would definatly be dropping.
An observer on the ground would see the bullet dropping straight down and the plane moving away.
Coolness list by 90cr500guy
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
Of course the tail gunner would see the bullets drop instantly. Friction aside, all objects fall towards the earth at the same rate of acceleration regardless of the speed they are traveling (~9.81 m/s if memory serves me correctly).
...say a second shooter shot a bullet out of the front of the plane, he would see his bullet fall just as fast as the tail gunner.
Even more lame...(ha!)...say a gunner in the plane has two bullets. He loads one in the gun, and keeps one is his hand. When he fires the gun, he happens to drop the bullet from his hand and out of the plane at the same exact instant. Result: both bullets will hit the ground at the same time.
...alright, enough for the day. I'm gonna go take recess in the WALLY WORLD section.
danjerman wrote:...say a second shooter shot a bullet out of the front of the plane, he would see his bullet fall just as fast as the tail gunner.
Nope the one out the front will fly just fine.
danjerman wrote:...Even more lame...(ha!)...say a gunner in the plane has two bullets. He loads one in the gun, and keeps one is his hand. When he fires the gun, he happens to drop the bullet from his hand and out of the plane at the same exact instant. Result: both bullets will hit the ground at the same time.
No.... the one he throws out the back will be moving forward due to the speed of the plane and will probably arc for awhile before dropping so the one from the gun will hit the ground first.
Coolness list by 90cr500guy
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
danjerman wrote:
...say a second shooter shot a bullet out of the front of the plane, he would see his bullet fall just as fast as the tail gunner.
Nope the one out the front will fly just fine.
danjerman wrote:
...Even more lame...(ha!)...say a gunner in the plane has two bullets. He loads one in the gun, and keeps one is his hand. When he fires the gun, he happens to drop the bullet from his hand and out of the plane at the same exact instant. Result: both bullets will hit the ground at the same time.
No.... the one he throws out the back will be moving forward due to the speed of the plane and will probably arc for awhile before dropping so the one from the gun will hit the ground first.
Ok, not sure where your logic is coming from but unless you are assuming that the bullet is entering low orbit than you are off your rocker.
Bullets don't "fly". There is no lift created by a typical bullet being fired out of a gun; they begin accelerating towards the earth the instant they leave the barrel. Unless you are assuming the bullet is rifled, then this may change the outcome slightly (less friction...duh). I really don't have the motivation right now to explain this all in great detail, but just because an object has a horizontal acceleration (strictly along the x-axis) does not affect the vertical acceleration (strictly along the neg y-axis) of gravity. If I had more time I could draw you a FBD on the bullet to explain this to you, but to be honest I'm too lazy. Plus, you can look in any 100 or 200 level physics book and find the same conclusion as I have mentioned above. Shit, even google the matter you'll find the same answers.
If you stick to the principle that everything falls at the same rate of acceleration, then you will see the light.
...I'm off to the beer fridge to try and kill the braincells I just used. Only the strongest survive!
danjerman wrote:If you stick to the principle that everything falls at the same rate of acceleration, then you will see the light.
What about a feather, sheet of paper or a leaf?
Jack Schitt
DIE FIRST, worry about it later!
DON'T talk about it, Just DO IT!
When in doubt, GO FLAT OUT!
2001 CR500R1 - SOLD
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Point taken and definatly worth thinking about but surely the forward momentum would have an effect on the dropped bullet vs the stalled one....
Momentum is a different subject, and will not affect its fall towards the earth. Either vector is pointing in a direction that does not cancel out the other.
danjerman wrote:
If you stick to the principle that everything falls at the same rate of acceleration, then you will see the light.
What about a feather, sheet of paper or a leaf?
These objects fall slower due to friction caused by air. Everyhting has the same pull from gravity...9.81 m/s^2, or 32.2 ft/s2 (i forgot the correct units when i mentioned this above!), but once air gets involved, the friction slows the fall to earth. Since we were talking a apples to apples in this example, it's a safe assumption to think that the friction caused by air would affect either the bullet equally.
If you were to put a penny and a feather inside a perfect vacuum, and drop either one at the same instant from...say...3 ft off the ground...or even 20 ft they would both hit the ground at the same exact time. Even if you swapped the penny for an M1 Abrams Tank, in a perfect vacuum they would both hit the ground at the same time.
Jack Schitt
DIE FIRST, worry about it later!
DON'T talk about it, Just DO IT!
When in doubt, GO FLAT OUT!
2001 CR500R1 - SOLD
2007 CR250R7 - SOLD
Wife and Daughter - Left Aug 17 - 2010
Jack Schitt - ??????????????
AlisoBob wrote:Steve, I'll take a .45 with me on the next flight to Phoenix.
You sit 10 rows behind me.
I'll stand up and take a shot at you.
The plane will be going 600mph forewards, the bullet will be going 840 feet per second ( or about 600mph backwards).
Lets see if it falls out of the barrel and lands on the floor, or splits your noggin' open.
The bullet would still split your head open. not because the bullet was going fast, if the speeds were matched, the bullet would actually stop, and your intended "target" would actually run into the bullet at 600MPH.
the same applies if you were going straight up. it isnt "ground speed" it is speed relative to zero movement in any direction.
same with a tailgun shooting rearward. if the gun fires twice the speed of the plane, then firing forward it would fire the planes speed plus the firing speed. firing backwards, it would subtract the plane's speed.
if the speeds were matched, then the bullet would "stop" and it would fall.
now keep in mind that firing at anything different than parallel with the direction of the plane introduces more variables...
ellett wrote:
So, using that obviously bong derived logic, if the plane can fly faster than the bullet and "you fire it towards the rear," the bullet will not only not "fall out of the barrel," but actually get pushed back into the shell casing?! Like the gunpowder isn't going to build any pressure in the barrel just because it's moving?
nope, if you fire a 500MPH bullet rearwards of a plane traveling 700MPH, then the bullet will still be traveling 200MPH forward (direction of the plane) relative to zero-movement.
Roostius_Maximus wrote:Maybee they magnatize the barrels to keep the bullet from falling out for shooting to the back
These threads are so stupid i dont even know where to start
nah, the bullets just shoot faster than the plane is moving, so they still "fly" backwards.
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