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| Topic: new theory about the orbits of the solar system | |
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Okay... The Bernoulli Effect influences drag. Rotation influences drag. The shape and rotation of a bullet reduces air resistance (drag) without necessarily generating lift. The bullet will fly farther, faster, and more accurately than a lead musket ball, given the same powder charge. So, Bernoulli's Principle is actually present in the case of a bullet because Bernoulli states a fluid's pressure will decrease simultaneously with a rise in the fluid's velocity. Furthermore, with a bullet's oblong shape and tapered tip, the twist rate of the rifling must be precisely calculated for the bullet's size. This is because the twist rate creates a balance of stability and instability of air pressures which allow the bullet to be more accurate (stability) while keep the tip pointed towards the target (instability) rather than up. This means modern bullets must take Bernoulli's Principle into account to prevent tumble (an oblique impact present more initial surface area, and thereby has less penetrating power). Another example: the dimples on a golf ball. They change the airflow around the ball to reduce drag, allowing the ball to travel farther and faster. What happens is, the dimples allow turbulent flow to be achieved behind the ball at a lower velocity. Once achieved, the flow is narrower than on a smooth ball, thereby reducing drag. As a further benefit, as the dimpled ball increases velocity, the turbulent flow changes very little meaning drag increases only slightly. This is just if the golf ball wasn't spinning, but Bernoulli's Law still applies here. The spin of the ball actually does generate lift, bringing a second application of Bernoulli's Principle into play. Finally, if velocity is zero, fluid pressure remains constant. If velocity rises, fluid pressure will drop accordingly (like a hurricane....low pressure, high winds). If velocity drops, pressure rises (the dog days of summer....Bermuda High, heavy stagnant air). This is all Bernoulli's Law states, but it veritably has a thousand uses and derivations. all true. but is the bernoulli effect happening aft of the point of separation of laminar flow on an aircraft wing? if the fluid, air in this case, is no longer being accelerated, which it's not as the boundary layer has separated and no longer adheres to the upper surface of the wing, does not airpressure above the wing equalize to the air pressure below the wing? the wing is stalled and still in motion but without the acceleration of air over the upper surface. how is bernoulli in effect without accelerating the fluid? Because Bernoulli's Law is still affecting air pressures even though lift is not being generated. Flight is only one application that is derived from Bernoulli's Law. Even when movement is zero, Bernoulli's still governs pressure. of course flight is only one application of the principle. so you're saying that on a standard atmospheric day at sea level with no wind, no movement of an airplane sitting on the ramp tied down, a perfectly calm day, the atmospheric pressure will be 29.92 inches of mercury below the wing of an airplane but will be less than 29.92"/hg above the wing? Any change in velocity (not acceleration) will cause a change in pressure. So from your wording, the air over the upper surface normally moves faster than the wing's velocity, hence the lower pressure on top. But Bernoulli's also tells us that the deceleration of air flow must cause air pressure to begin rising again, even if to create equilibrium between two air flows. Bernoulli's is not all about lift.
all true. velocity is key. i mentioned accelerated air as relative to it's speed before it came in contact with the leading edge of the wing and flowing over the wing as opposed to the air fowing under it. you can say all day long that the principle applies to other than airplane flight and i'll agree all day long but the topic has turned to airplane wings. still, in the standard day i mentioned above with nothing having velocity rlatively different from anything else, where is the bernoullii affect on air pressure? i didn't mention lift. the principle doesn't mention lift. it only mentions pressure changes relative to velocity changes of a fluid. if all velocities are zero and unchanging, where's the change in pressure??? When I am running, Bernoulli's applies to me as well. It's why I hear wind in my ears when I run, and that only happens once I reach a certain speed. It never happened when I was a child because I couldn't run fast enough. When I grew 8 inches in one year, the longer stride allowed me to achieve a faster speed....and that's when I could hear the wind in my ears. It's the lower air pressure from the increased velocity that creates the wind noise, just like the whoosh of a swinging bat.
so what you hear when running is due to bernoulli effect? can't be due to the effect of drag? in this case form drag? or as ears are appendages that stick out perhaps parasite drag works. drag increases proportionally with the square of the airpeed increase. double the airpeed, quadruple the drag coeficient. walk at 2 mph in a calm wind you'll hear little wind noise. run at 4 mph and you'll hear four times the wind noise. |
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jr is right, you have to consider the weight of the asteroid, the speed, and the gravitational pull of the earth or larger body. it is the same reason a bullet will travel in a straight line until it slows down enough for gravity to pull it down. Actually the bullet is falling towards the center of the Earth at 32 ft/sec squared the instant it leaves the barrel of the gun. Speed has nothing to do with it. The bullet never travels in a straight line, it travels in a ballistic curve. dead wrong. if a bullet is fired from a height of four feet and doesn't hit the ground for four seconds how does that equate to falling at thrty two feet/second/second? it fell at an average rate of one foot per second and it hardly feel thirty two feet in the first second as you suggested. it requires drag to slow it down enough to fall to earth. that is the reason for the balistic curve. but suppose you fired the bullet on the moon? would it travel in the same balistic curve and impact the moon's surface in the same distance? if i drop a feather in earths atmospere will it accelerate to thirty two feet per second in the first second? of course not. drag comes into play no? You couldn't be more wrong. This is simple high school physics. Look it up. If a bullet is fired from four feet and is not pointed UP, but horizontal, it will take EXACTLY the same time to hit the ground as one dropped from four feet. The only exception to this is the curvature of the Earth must be taken into account for complete accuracy. not so. what you describe is the force of gravity on the bullet but not the vertical velocity of the bullet. are you really saying that a sniper's bullet fired from two thousand yards will take no longer to impact the ground than the same bullet dropped from shoulder height? what you have not considered is the speed of the bullet and how the atmosphere affects it. fire a bullet straight out in front of you at a height of four feet and at the same time drop a bullet from four feet and tell me that they will both hit the ground at the same time. or make it easier on yourself. throw a baseball or a rock and drop another. then ask pudge rodriguez to throw a baseball as hard as he can as though he's gunning down a-rod attempting to steal second and you throw a ball at the same time and tell me that pudge's cannon shot wasn't still sailing into center field when yours hit before clearing the infield dirt. an airplane in straight and level unaccelerated flight has the same force of gravity acting upon it as does the bullet or the feather along with the force of drag, lift and thrust. so why does the airplane not fall to the ground accelerating downward at 32'/sec2? the reason is lift counters gravity equally the force of lift being exerted on the wing through the fluid dynamics created by the air flowing over and under it. reduce thrust without changing pitch angle of attack and you lessen the force of fluid dynamics over the wing and the force of gravity exceeds lift and the aircraft decends. but the descent is readily controlled and the airplane will not accelerate downward at 32'/sec2. a sky diver will accelerate at 32'/sec2 only until he reaches terminal velocity which is dictated by the density of the atmosphere and his body position. the same forces act on a bullet as acto on the airplane or the skydiver although the initial thrust is momentary where the thrust of an aircraft is available as long as their is fuel to burn to maintain thrust. why does a glider stay aloft for much longer when released from a tow plane than a brick dropped at the exact moment from the same tow plane. the reason is that the glider has much better aerodynamic characteristcs than does the brick just as a speeding bullet has better aerodynamic characteristics than a bullet with zero horizontal speed. you're simply still dead wrong. and the curvature of the earth has no more effect on the bullet than it does on an aircraft flying from san francisco to paris as far as the effects of gravity are concerned. Just a reminder! since you seem to have forgotten what you wrote. |
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i remember well what i write.
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i remember well what i write. Apparently not. |
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The fired bullet will just be further away from the source when it hits.
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Edited by
jrbogie
on
Tue 08/16/11 02:31 PM
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and takes a longer time to hit. but how does any of this have anything whatsoever about this new "theory" of the solar system???
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I was wondering when someone would bring that up.
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I skimmed some parts of this thread, and from what I can see MetalWing is correct.
--------- I haven't watched the videos, but we have known for a long time that the planets move in slightly spiraling, precessing ellipses. Tidal effects require a transfer of energy from one aspect of the system to another, so we would not expect the distance between orbiting planetary bodies to remain perfectly fixed. I have heard (unverified) that the moon is moving away from the earth at a pace of a few centimeters per year. |
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I skimmed some parts of this thread, and from what I can see MetalWing is correct. --------- I haven't watched the videos, but we have known for a long time that the planets move in slightly spiraling, precessing ellipses. Tidal effects require a transfer of energy from one aspect of the system to another, so we would not expect the distance between orbiting planetary bodies to remain perfectly fixed. I have heard (unverified) that the moon is moving away from the earth at a pace of a few centimeters per year. so if MW is correct and velocity has no effect on gravitational pull, why then is the moon moving AWAT from earth? why does any planet remain in orbit about the sun???? |
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and takes a longer time to hit. I just want to be clear....are you claiming that a bullet fired with ZERO vertical component to its velocity will take longer to descend a fixed distance from its vertical starting position than a bullet dropped from the same height takes to descend the same distance? (I don't mention 'striking the ground' because, as metal wing pointed out, due to curvature of the earth even perfectly flat ground will drop slightly away.) |
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and takes a longer time to hit. I just want to be clear....are you claiming that a bullet fired with ZERO vertical component to its velocity will take longer to descend a fixed distance from its vertical starting position than a bullet dropped from the same height takes to descend the same distance? (I don't mention 'striking the ground' because, as metal wing pointed out, due to curvature of the earth even perfectly flat ground will drop slightly away.) that's what i'm saying. you can try it. fire a bullet level to the ground an inch off the ground, drop another bullet from an inch off the ground. time them both to ground strike. then tell me which one took longer to strike the ground. but again, none of this has a thing to do with planatery orbit as the atmospere does play a role in the bullet example. though not much. so why do planets remain in orbit about the sun if the suns gravity is the only force acting on the planets? does the velocity of the planet have nothing to do with it remaining in orbit? the sun's gravity is constant. so why has every planet not crashed into the sun? |
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I skimmed some parts of this thread, and from what I can see MetalWing is correct. --------- I haven't watched the videos, but we have known for a long time that the planets move in slightly spiraling, precessing ellipses. Tidal effects require a transfer of energy from one aspect of the system to another, so we would not expect the distance between orbiting planetary bodies to remain perfectly fixed. I have heard (unverified) that the moon is moving away from the earth at a pace of a few centimeters per year. so if MW is correct and velocity has no effect on gravitational pull, why then is the moon moving AWAT from earth? why does any planet remain in orbit about the sun???? I see three parts to your question, and I'm not sure what relationships, if any, you are suggesting may or may not exist between those parts. I have a feeling (?) that you have taken MW's words out of context. I don't believe he was claiming there is never any kind of significant interplay between the effects of horizontal velocity and the effects of vertical acceleration - only that the acceleration due to gravity at any point in time depends entirely on factors *other* than velocity. He is correct. Why does a planet remain in orbit? My vague memory suggests this is because the tendency of an object to 'fall' towards the other body (under the influence of gravity) is almost-exactly matched by the tendency of the object to fly away (due to velocity). Horizontal velocity does NOT negate nor change vertical acceleration. Orbits are special cases where those two separate factors are in balance with each other. This brings us back to Metal's early comment about 'the curvature of the earth'. We all agree that the curvature of the earth can cause a delay in how long the bullet takes to hit the earth, but NO delay how long it takes the bullet to descend a fixed distance from the straight line it was fired along. If we had no atmosphere, and if you fired a bullet perfectly horizontally *fast enough*, you could send that bullet into an orbit (at only 4' off the ground, you should do this on a mountain top or the orbit would be short lived), but gravity would still act on that bullet in exactly the same way as a dropped bullet. Think of it this way: both dropped and fired bullets fall towards the earth with the same acceleration - but if you fire a bullet from the top of a mountain you would expect it to take longer to hit simply because it has farther to fall, right? The same kind of thinking applies to sending a bullet into orbit - except the 'drop off' from the perfect horizontal continues endlessly as your orbit the earth. |
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and takes a longer time to hit. I just want to be clear....are you claiming that a bullet fired with ZERO vertical component to its velocity will take longer to descend a fixed distance from its vertical starting position than a bullet dropped from the same height takes to descend the same distance? (I don't mention 'striking the ground' because, as metal wing pointed out, due to curvature of the earth even perfectly flat ground will drop slightly away.) that's what i'm saying. you can try it. fire a bullet level to the ground an inch off the ground, drop another bullet from an inch off the ground. time them both to ground strike. then tell me which one took longer to strike the ground. but The tiniest error in vertical acceleration would have a huge effect in the outcome of this test. While I'm always a fan of do it yourself physics tests, this one requires the most careful calibration. Do you have the proper equipment for this? I don't. One could also just use objects of lower velocity. I actually have done this test with objects of lower velocity, and found metalwing to be correct. so why do planets remain in orbit about the sun if the suns gravity is the only force acting on the planets?
Lets consider a two body system of inert objects in a vacuum instead of the planetary system; we can put one in orbit around the other with the force of gravity between them being the only force present. I somewhat explained this in another post, we may be able to explain it more fully if you like. (If we consider the actual entire solar system, then we can't say things like "the only force" acting...) does the velocity of the planet have nothing to do with it remaining in orbit?
Velocity has a lot to do with it remaining in orbit, and nothing I've read from MW contradicts this. the sun's gravity is constant. so why has every planet not crashed into the sun?
Does my earlier post clarify this? |
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I can't watch videos today, but I looked up the MB episode on wikipedia. A bullet fired horizontally and one dropped from the same height will hit the ground simultaneously. Confirmed Adam and Jamie first carried out two small-scale experiments, one using ball bearings (dropped vs. shot from a spring-loaded launcher), the other using paintballs (dropped vs. fired from a paintball gun). While the first experiment seemed to bear out the myth, the second one contradicted it; Adam attributed this result to imperfections in the paintballs' surfaces that caused them to veer slightly off course.
For full-scale testing, they started at a firing range and used a .45 caliber pistol to measure the distance a bullet would travel before hitting the ground. Since the ground there was not level, they set up a second test at Fort Mason. Once they had properly fine-tuned their mechanism to fire and drop the bullets at the same time, they found that the two bullets landed within 39.6 milliseconds of each other. Commenting that this difference was less than the duration of one film frame (shot at 24 frames per second), and thus short enough for the human eye not to notice, they declared the myth confirmed. More to the point, 39.6 ms is probably well within expected experimental error. While their 'conclusion' matches MW's and my own, I don't consider this MB episode to be particularly strong evidence on its own. How did they go about minimizing their vertical velocity component? How long was the barrel? What 'error' did they estimate for this part of their experiment? However, the entire history of manned flight, the space program, ballistics, astronomical observations, etc gives us, collectively, much stronger evidence for the claim. |
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There were a number of incorrect statements made early in this thread and I was trying to paint a broader picture of how it all fits together.
A comet would not be mistaken for a neutron star because the same equations that dictate the falling-fired bullet effect would affect the ballistics of a comet, dark star, frozen apple, and anything else. The effect on the orbits of other bodies in our solar system would quickly show indications of a high mass object like a brown dwarf. There really is no "new theory". The guy in the video is just restating various things that are already known as if they were new discoveries. The "electric" properties were misstated and taken out of context. The Sun does not drag the planets into a spiral orbit around the galaxy. All the planets and the Sun are affected equally by the galaxy's gravity ... just like the bullet dropped vs the bullet fired. All objects in our solar system are in orbit about the Milky Way. |
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Edited by
jrbogie
on
Tue 08/16/11 05:34 PM
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Lets consider a two body system of inert objects in a vacuum instead of the planetary system; we can put one in orbit around the other with the force of gravity between them being the only force present. I somewhat explained this in another post, we may be able to explain it more fully if you like (If we consider the actual entire solar system, then we can't say things like "the only force" acting...). the planetary system operates in a vaccum. never suggested an "only force." been saying all along the force of momentum do to the velocity of the planets is also in play. Velocity has a lot to do with it remaining in orbit, and nothing I've read from MW contradicts this.
then you've been reading differently than what i've been reading. |
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As jrbogie has indicated in every post, he does not agree with (understand) the physics behind why the bullet shot/bullet dropped effect. The physics behind this event are the same as what causes moons to orbit, comets to take their trajectory, etc.
Velocity is all about trajectory of course but the concept that no matter what the velocity is, the acceleration of gravity is the same for all objects at that same distance from a mass. That is why an object with a horizontal velocity which gives a ballistic curve equal to the curvature of the Earth will orbit. |
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Lets consider a two body system of inert objects in a vacuum instead of the planetary system; we can put one in orbit around the other with the force of gravity between them being the only force present. I somewhat explained this in another post, we may be able to explain it more fully if you like (If we consider the actual entire solar system, then we can't say things like "the only force" acting...). the planetary system operates in a vaccum. never suggested an "only force." been saying all along the force of momentum do to the velocity of the planets is also in play. I'm really not trying to bicker, only to illustrate the deliberateness of my phrasing. Yes, of course you never suggested that that gravity was 'the only force acting', but you question the claims of others while representing them as implying that the 'gravity of the sun is the only force acting' on the planets. so why do planets remain in orbit about the sun if the suns gravity is the only force acting on the planets?
This immediately creates some problems, because in reality the gravity of the sun is not the only force acting on any of the planetary bodies - and neither MW nor myself has implied otherwise. What we did do was make assertions about gravity affecting the descent of two objects equally, independent of their horizontal velocity. In our actual solar system every planetary body is effected by every other planetary body - not just the gravity of the sun, so naturally your quote above does not reflect my belief (nor, i presume, MW's). Since you misrepresented our claims in this way, I wanted to contrive a scenario in which that misrepresentation would actually be close to the truth. We find this in a two-body problem in a true vacuum. The planets don't move in a true vacuum. Though we can probably (?) completely disregard the solar wind while calculating the future orbit of the planets for a hundred years, we cannot deny that technically the solar wind does apply some tiny amount of force. So we have to differentiate between the idealized vacuum situation and the reality of the solar system before we can use the phrase "only force acting". These were my thoughts behind the phrasing that I chose. Lets consider a two body system of inert objects in a vacuum instead of the planetary system; we can put one in orbit around the other with the force of gravity between them being the only force present.
Velocity has a lot to do with it remaining in orbit, and nothing I've read from MW contradicts this.
then you've been reading differently than what i've been reading. I agree that we have been reading differently. I'm sure there are statements in this thread that are open to multiple interpretations, but nowhere has metalwing unambiguously contradicted this basic claim. If you think otherwise, maybe you read something into his words that weren't there. |
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an object with a horizontal velocity which gives a ballistic curve equal to the curvature of the Earth will orbit.
That's a delightful simple and concise way of expressing this; it took me several paragraphs to try to express that. |
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