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Old 25-04-2012, 10:18
PencilBreath
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...that is travelling at 200mph, do you land in exactly the same spot?

Also, if the cargo is birds that weigh about 1 ton when "perched", would it save fuel to keep them all airborne during the flight?
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Old 25-04-2012, 10:20
~Twinkle~
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If you jump in a plane does it make the load any lighter for that second when you're suspended in mid-air?
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Old 25-04-2012, 10:20
Kapellmeister
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...that is travelling at 200mph, do you land in exactly the same spot?
I assume so, but I don't know why.
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Old 25-04-2012, 10:24
gulliverfoyle
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of course

everything is about relative velocity and newtons laws of motion

remember we are sat on a spinning globe, orbiting about a star etc etc
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Old 25-04-2012, 10:27
Helbore
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of course

everything is about relative velocity and newtons laws of motion

remember we are sat on a spinning globe, orbiting about a star etc etc
Not true. I just jumped on the spot and now I'm on Venus.

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Old 25-04-2012, 10:28
MidnightFalcon
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...that is travelling at 200mph, do you land in exactly the same spot?

Also, if the cargo is birds that weigh about 1 ton when "perched", would it save fuel to keep them all airborne during the flight?
When you jump you are already travilling forward at 200 mph relative to the outside world (0mph relative to the plane). Inertia will maintain this relative speed for the second or so it takes you to land on the floor again.


(I think).
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Old 25-04-2012, 10:28
~Twinkle~
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of course

everything is about relative velocity and newtons laws of motion

remember we are sat on a spinning globe, orbiting about a star etc etc
If gravity suddenly disappeared, would we all simply go flying off into space?
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Old 25-04-2012, 10:29
PencilBreath
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How about the birds though, if they remain in flight during the journey, do they add to the aircraft weight?
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Old 25-04-2012, 10:31
MidnightFalcon
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How about the birds though, if they remain in flight during the journey, do they add to the aircraft weight?
Assuming they are caged and already moving at a speed relative to the plane - where would they fly to?
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Old 25-04-2012, 10:32
Sea_salt
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...that is travelling at 200mph, do you land in exactly the same spot?
If the plane's not accelerating or slowing down, then yes.
Also, if the cargo is birds that weigh about 1 ton when "perched", would it save fuel to keep them all airborne during the flight?
No.
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Old 25-04-2012, 10:33
PencilBreath
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Assuming they are caged and already moving at a speed relative to the plane - where would they fly to?
Well, practicalities aside, how about they just fly in little circles lol.
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Old 25-04-2012, 10:37
ubanjod
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Someone needs to revisit GCSE physics

How about this OP, have you thought about walking towards the front of the plane? That would mean your actually walking faster than the plane is flying
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Old 25-04-2012, 10:38
MidnightFalcon
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Well, practicalities aside, how about they just fly in little circles lol.
A tons worth of birds all flying in little circles at the same time? You would need a bloody big cargo hold.

In this case I assume the weight of the plane would be affected though I'm not sure what the effect of a million pairs of wings creating a downforce in the hold would be.
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Old 25-04-2012, 10:39
Helbore
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If gravity suddenly disappeared, would we all simply go flying off into space?
We'd be fine until the next time we tried to walk (or otherwise push against some object like the surface of the Earth)
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Old 25-04-2012, 10:41
Nard Dog
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is this 1974?
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Old 25-04-2012, 10:41
MidnightFalcon
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We'd be fine until the next time we tried to walk (or otherwise push against some object like the surface of the Earth)
Or until the all the matter in all the suns in the universe started to disperse. That might cause a few problems.
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Old 25-04-2012, 10:43
~Twinkle~
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No, but I wish it was. I might know a bit more about physics had it been 1974, it wasn't a subject that I was taught at school.
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Old 25-04-2012, 10:47
Moony
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We'd be fine until the next time we tried to walk (or otherwise push against some object like the surface of the Earth)
Is that true though - wouldn't the centripetal force that acts on our bodies due to the rotation of the earth and gravity cause us to fly off at a tangent when gravity was removed (much like spinning a ball on the end of a piece of string experiment). Removing gravity would be like cutting the string would it not?

Isn't that the reason sea launching rockets near the equator is so attractive - they get an extra boost from the rotation of the earth.

http://en.wikipedia.org/wiki/Sea_Lau...based_launches
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Old 25-04-2012, 10:48
Throgmorton1
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A plane is an enclosed space - so the birds weight would be the same whether they were flying or perched - the same goes for the flapping of wings - no effect at all on the plane.

If you jumped straight up - you would land in the same place on the plane - the plane would have moved though - so would you as part of the plane.

That all makes sense to me - but I can't quite get my head around the fact that you are travelling at the speed of the plane and can't go faster. It seems more logical to me that if I threw a paper plane inside a plane - it would be going faster. I know it's not true - but that doesn't make it logical.
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Old 25-04-2012, 10:51
juliancarswell
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surely its also about air friction. If you were stood on the roof of the plane at 200 mph (assuming you could) and jumped on the spot, you would probably hit the tail of the plane before your feet touched down again.
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Old 25-04-2012, 10:57
Throgmorton1
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surely its also about air friction. If you were stood on the roof of the plane at 200 mph (assuming you could) and jumped on the spot, you would probably hit the tail of the plane before your feet touched down again.
If you could jump off the roof - then you would no longer be a part of the plane - so you wouldn't land in the same spot
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Old 25-04-2012, 11:00
Moony
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That all makes sense to me - but I can't quite get my head around the fact that you are travelling at the speed of the plane and can't go faster. It seems more logical to me that if I threw a paper plane inside a plane - it would be going faster. I know it's not true - but that doesn't make it logical.
It all depends on which frame of reference you measure your speed from.

If you walked at 4 mph from the back to the front of the plane that was travelling at 500mph - you are travelling at 4mph relative to the plane and all the passengers on it. To you it also feels like 4mph because of your frame of reference and an observer on the plane would observe your speed to be 4mph

To an observer on the ground though - you would be observed to be travelling at 504mph.

Both observers would be correct.
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Old 25-04-2012, 11:02
RobinOfLoxley
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The Military were interested in Concorde initially. But they realised that Concorde travelled faster than a speeding bullet. Concerns about it shooting itself down meant the idea was shelved.
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Old 25-04-2012, 11:05
Throgmorton1
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It all depends on which frame of reference you measure your speed from.

If you walked at 4 mph from the back to the front of the plane that was travelling at 500mph - you are travelling at 4mph relative to the plane and all the passengers on it. To you it also feels like 4mph because of your frame of reference and an observer on the plane would observe your speed to be 4mph

To an observer on the ground though - you would be observed to be travelling at 504mph.

Both observers would be correct.
Sounds fine - but it's not true - you would be travelling at the speed of the plane to an observer on the ground - movement inside the plane won't get you to your destination any faster,
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Old 25-04-2012, 11:10
bobcar
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Sounds fine - but it's not true - you would be travelling at the speed of the plane to an observer on the ground - movement inside the plane won't get you to your destination any faster,
It is correct, to the observer on the ground you will be going at 504 mph. When you reach the front and stop you will again be going at 500 mph, walking back to your seat you will be going at 496 mph.
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