Tomnova16
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Registered: 21st Jan 06
Location: Gerrards Cross Drives: Porsche 911
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stephen fry said it would weigh the same on QI
to do with the total mass, if it was open top then it would be different
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pow
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Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
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I remember that QI
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BluKoo
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Registered: 8th Apr 02
Location: Stonehaven (Scotland)
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When the pigeons fly they force air downwards. The force/weight of that air would be equal to or greater than the weight of the pigeon. Therefore there would be no difference.
[Edited on 25-10-2012 by BluKoo]
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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Assuming the truck is completely air tight.
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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What if the pigeons were kept up by helium bags then it couldn't weigh the same.
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John
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Registered: 30th Jun 03
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It's nothing to do with the truck being air tight, it's all simple physics but mythbusters have done it in practice, as said.
Noob question tbh.
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3CorsaMeal
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Registered: 11th Apr 02
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Steve will soon be offering passenger laps to pigeons.
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Toby
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Registered: 29th Nov 05
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quote: Originally posted by Welsh Dan
Season 5, Episode 8. Can't find it on the toob. I think the result was that it still weighs the same, as there is a downforce exerted by the birds wings.
Thats surprising that a bird can provide its own weight in downforce.
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Gary
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Registered: 22nd Nov 06
Location: West Yorkshire
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How else would it fly?
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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You would have thought that it would only apply an equal force on the direct air around it and that the force would disperse.
Same as a bird flying above the ground wouldnt be exterting a force on the ground only on the air around it, and the same way the further you stand away from a jet engine the less you feel it.
Id imagine for this scenario the truck would have to be air tight
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Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
User status: Online
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It doesn't scale though, if you had a massive box with them in, how on earth is the air going to affect the bottom? Or is this an Doric speech of Syracuse question?
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Bonney
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Registered: 14th Nov 04
Location: St Helens
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Heres one, Does a tanker full of helium weigh less than an empty tank? (As it is lighter than air)
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Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
User status: Online
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If its sealed, yes, hence why airships float, because the lift from the contents overcomes the weight of the structure.
I just couldn't see how the birds thing would work, I can see the theory but just couldn't see it working. Like if the bird stopped flying and became a missile, would the truck get heavier just before the bird hits the floor?
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ed
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Registered: 10th Sep 03
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Weight is the force of an object due to gravity. Reduce the mass, reduce the weight. The tanker would weigh less if it had a tank full of helium, just as it would weigh more if it had a tank of water.
You answered it by telling us helium weighs less than air anyway.
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ed
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Registered: 10th Sep 03
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The pigeons one is simple if you think about it rationally too. People seem to think that flight is this magical thing and that air is not real - think of something that flys as a boat and the air as water. If the truck was on a weigh bridge and had a boat floating in said water, you wouldn't think that the boat was exerting no force on the truck would you.
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Bonney
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Registered: 14th Nov 04
Location: St Helens
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Wander how it would wash with VOSA with the pidgeons,
"Drive, Your overweight need to unload a few"
"You sure officer, i was the right weight when i set out, the feckers must ave jumped!"
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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quote: Originally posted by ed
The pigeons one is simple if you think about it rationally too. People seem to think that flight is this magical thing and that air is not real - think of something that flys as a boat and the air as water. If the truck was on a weigh bridge and had a boat floating in said water, you wouldn't think that the boat was exerting no force on the truck would you.
water is different from air like a solid is different from water. The molecules are further apart in air than water, and hence wont transfer forces in the same way. Exactly like your brakes are spongy when they have air in them
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