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I haven't read all the posts, but my first thought was 'curvature of the earth'
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I've read the whole thread.
Very pleasing :) and entertaining. fwiw, you fire Cannonballs from Cannons. |
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just for the record naydam. the relative density of air above and below a golf ball would be minimal. i would've guessed that spinning would occur for one of two reasons:
a) the ball is not hit dead center b) even if it was hit dead center and there was no spinning, it would create spin by friction with the air, the nature of this spin would be pretty random as a guess if the ball was hit horizontally. But as a golf ball is normally hit upwards, i'm guessing it would normally have "backspin". Can't quite work out why that would be, but i'm pretty sure that is the case. |
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I think the best answer given is by honest novice above. But as sparky and others have mentioned there will be loads and loads of forces in play, but the main two are gravity and air resistance.
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how can a thread like this go on so long :^0
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we did a module, final year of uni, called "Theoretical Mechanics" Was all about the Coriolis force. I couldn't get to grips with it - I think i'd reached the limits of my mind by that point. Did you ever do stuff about the Coriolis force Honest Novice? I'm pretty sure they'd have to take that into account whenfiring rockets and that all the way around the world.
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From sparky's link:
Coriolis drift The Coriolis effect causes drift related to the spin of the Earth, known as Coriolis drift. Coriolis drift can be up, down, left or right. Coriolis drift is not an aerodynamic effect. It is a result of flying from one point to another across the surface of a rotating sphere (Earth). For small arms, this effect is generally insignificant, but for ballistic projectiles with long flight times, such as extreme long-range rifle projectiles, artillery and intercontinental ballistic missiles, it is a significant factor in calculating the trajectory. The coordinate system that is used to specify the location of the point of firing and the location of the target is the system of latitudes and longitudes, which is in fact a rotating coordinate system, since the Earth is a rotating sphere. During its flight, the projectile moves in a straight line (not counting gravitation and air resistance for now). Since the target is co-rotating with the Earth, it is in fact a moving target, relative to the projectile, so in order to hit it the gun must be aimed to the point where the projectile and the target will arrive simultaneously. When the straight path of the projectile is plotted in the rotating coordinate system that is used, then this path appears as curvilinear. The fact that the coordinate system is rotating must be taken into account, and this is achieved by adding terms for a "centrifugal force" and a "Coriolis effect" to the equations of motion. When the appropriate Coriolis term is added to the equation of motion the predicted path with respect to the rotating coordinate system is curvilinear, corresponding to the actual straight line motion of the projectile. For an observer with his frame of reference in the northern hemisphere Coriolis makes the projectile appear to curve over to the right. Actually it is not the projectile swinging to the right but the earth (frame of reference) rotating to the left which produces this result. The opposite will seem to happen in the southern hemisphere. The direction of Coriolis drift depends on the firer's location or latitude on the sphere, and the azimuth of firing. The magnitude of the drift depends on the location, azimuth, and time of flight. The Coriolis effect is at its maximum at the poles and negligible at the equator of the Earth. The reason for this is that the Coriolis effect depends on the vector of the angular velocity of the Earths rotation with respect to xyz - coordinate system (frame of reference).[18] |
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you didn't get on to the coriolis force until your final year?
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yep. Mechanical Engineering. What course did you do~?
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Hi Rob
We did cover Coriolus force and its proof by first principles. I was very average at Uni . Absoletely certain without google I could no longer do that. Heck I sound a bit like Kermit the frog who sat half way up the stairs. I feel for folk who are |
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nice one honestnovice.
:) |
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I must say I am rather disappointed that certain forum members have expressed their surprise that this thread has lasted nearly 300 posts. I am a very interesting person and people hang on my every word don't you know - you only have to look at my quizzes to realise how popular I am, the last one went on for three days!
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Robdylan. I've just googled 'Golfball flight' and learned quite a lot. The golfball has BACKspin which is caused by being hit with the golf stick. About 5,000rpm, apparently. This causes all sorts of wierd and wonderful laws to come into play. But my theory should have caused FORWARD spin and my dimple theory is 'up the Swanee' too.
My only remaining straw within grasping range is that the original question precludes the use of a golf stick, so there would be no initial imparted spin at launch time. Didn't see any data for what would happen to a golf ball with no initial spin. I agree, though, that there has been some bloody good theorising and ideas bandied about. A step up from fart-sniff. :-) |
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just got back from a session naydam. yep, everything that is good and bad about chitchat has been found on this thread imo.
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interesting thread, yet no one could solve the "Cecil Rhodes" crossword clue
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golf stick!!!!
oh gawd ... orioles will crucify you :( |
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Fact!
the golf ball dropped would hit the ground first. The wind pressure on the ball hit horizontaly would create upwards drag. Stick ure hand out your car window when driving and it willl lift in the air. Esp more so as the dimples on golf balls exagerate this lift. |
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if you dropped a golf ball an a bowling ball form the same height they would hit the ground at the same time
the ball that is fired will take longer to drop |
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THANKS FOR CLEARING THAT UP
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The fired ball has longer to drop because of Earth's curve.
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This thread reminds me of Karl Pilkington's utter refusal to understand the nature of infinity, "how would they know if they'd made a mistake".
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Infinity is easy to grasp id you think of everything as cyclical.
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*if
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Maleuk. Why should it lift? Formula 1 cars use the same phenomenum to create downforce.
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That doesn't mean they stick their hands out! :-)
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phenomenum
(ba dee bedebe) phenomenum (ba debe dee) phenomenum (ba dee bedebe badebe badebe dee dee de-de de-de-de) |
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Sparky. It was that or 'thing'. Mind you, I can spell 'thing'. :-)
Effect!! That's the word I wanted. Damn! |
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I was talking to a friend of mine this evening, who did a DPhil at Oxford. He's a physicist and I mentioned this thread (God help me - I haven't spoken to him in ages, but he lives abroad and I'm due in the area next month and thought I'd drop in. I rang to arrange things and we spent 10 minutes talking about a thread on Chit Chat!)
He gave me the answer :) |
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i'm not getting involved.
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Why does this thread have 309 replies please?
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Because our education system is failing.
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Hardly think chit chat is going to educate the nation.
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That could be the forum motto.
'Chit Chat, education for the nation.' I'll get me mortarboard. |
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This has to be a gag yes?
If there is force a horizontal trajectory would delay the gravity effect. The fired ball (whether upwards or horizontal) would take longer to fall. |
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What if it was fired straight out (not angled into the air)?
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So, are we all agreed that the fired ball would take slightly longer now? (Assuming that it didn't land on higher ground somewhere)?
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what about if you had a van packed with 1000 parrots all sitting on perches attached to the van , then weighed the van . the someone fired a gun and the parrots were no longer sitting on their perches but in the air in the van , would the van weigh the same ??
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ENGLANDAWAY 10 May 00:43
If there is force a horizontal trajectory would delay the gravity effect. Good Lord :( |
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oh sorry thought this was a dom deluise tribute thread
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dead pop stars 10 May 08:46
what about if you had a van packed with 1000 parrots all sitting on perches attached to the van , then weighed the van . the someone fired a gun and the parrots were no longer sitting on their perches but in the air in the van , would the van weigh the same ?? no |