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dell


Member

Posted Sun Feb 14th, 2010 11:10am Post subject: QI- It's wrong!

hello.on QI stephen said you could drop a hammer and a feather at the same time and they would land at the same time my mum tried this and the hammer dropped first....any clues...


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Laur1991


Member

Posted Sun Feb 14th, 2010 11:29am Post subject: QI- It's wrong!

Yeah, I'm not sure why they used a feather as an example, because pretty much everyone knows they float downwards...

@Lauren1991

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gjhsu


Moderator

Posted Wed Feb 17th, 2010 5:21am Post subject: QI- It's wrong!

If you drop them in a vacuum, they will land at exactly the same time. Point of the segment on QI being that the acceleration from gravity is constant, regardless of mass.

This is shown by the Apollo 15 clip where the feather and hammer are dropped.


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Marty10000


Member

Posted Tue Feb 23rd, 2010 8:54am Post subject: QI- It's wrong!

As usual, physicists will say this hold true under the following conditions;

1) friction does not happen
2) this is performed in a vacuum
3) the body of mass they are dropped towards is a uniformly dense perfectly formed sphere that is of a mass much greater then the hammer or feather (other wise the mass the hammer and feather are falling toward would be pulled toward the heavier of the two and hence it would appear to fall faster)

The concept this experiment is supposed to convey is that the force exerted by the earth on other objects is proportional to the mass of the object, and so is the acceleration.

Force = Mass X Acceleration
Force of Earth on objects near the surface = Mass of object X 9.8 meters per second per second
Therefore
Mass X Acceleration = Mass of object X 9.8 meters per second per second
And so...
Acceleration = 9.8 meters per second per second
Regardless of the masses of the objects, they always fall at the same speed, provided the above conditions apply.
This is why astronauts demonstarted this in space, where these conditions are nearly met.


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khobman12


Member

Posted Tue Feb 23rd, 2010 10:41pm Post subject: QI- It's wrong!

I think they made it quite clear in the programme that it was in a VACUUM!


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F A


Member

Posted Sun Mar 7th, 2010 10:28pm Post subject: QI- It's wrong!

Here in France we have a former Education Minister and geologist who got himself ridiculed for not knowing that. A controversy is now in full swing because he has just published a book questioning global warming which happens to contain many mistakes...
(Hello everybody, I'm new here.)


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Nicklezz


Member

Posted Mon Mar 8th, 2010 12:02pm Post subject: QI- It's wrong!

Getting an opportunity to correct Stephen Fry is like winning the Jackpot. I suspect it doesn't happen very often! I'm expecting the newspaper to visit at any time in fact!

Anyways! I'm one of the "special" people - yes that's right...I'm a Trekker. And naturally I'm glued to the TV set when you start debating anything connected with astronomy, ready to nitpick in a way only we can.

In the last QI you (Stephen) said: "sucked into a vacuum". This is a common mistake as most people connect "vacuum" with their old Hoover at home. Fact of the matter is that a vacuum is NOTHING and therefore it has no power to suck anything. You are actually blown into a vacuum from the air filled space you start out in (like a space ship). You'll find people claiming the opposite - but they're wrong...and most likely Star Wars fans! ;P

Thomas
Norway

Where ever you go - go with all your heart!

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gjhsu


Moderator

Posted Mon Mar 8th, 2010 10:18pm Post subject: QI- It's wrong!

Or you could just say it's a simple matter of equalizing pressure. Whether being sucked or blown (er, behave...), it's a matter of perspective. In any case, it's one high-pressure volume moving to a low-pressure volume.


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Nicklezz


Member

Posted Tue Mar 9th, 2010 12:11am Post subject: QI- It's wrong!

Indeed! Equalizing pressure is absolutely right, BUT - suction is still out (and I don't say that very often I'm ashamed to admit). In fact there is no such thing as suction. Only teasing a pressure to "equalize"…which is not very sexy, rather depressing and does nothing to equalize MY pressure as a Frysexual.

Where ever you go - go with all your heart!

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unfamiliarname


Member

Posted Tue Jun 8th, 2010 3:22am Post subject: QI- It's wrong!


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unfamiliarname


Member

Posted Tue Jun 8th, 2010 3:27am Post subject: QI- It's wrong!

khobman12 said:
I think they made it quite clear in the programme that it was in a VACUUM!

Actually, at no point was the term "vacuum" used, nor even the term "theoretical", unless I've seen a very badly edited version! So not entirely accurate, rather than wrong, perhaps. Certainly QI is quite a long way from infallible - the most obvious example that springs to mind being the "Mithras" Christmas stuff several years back: based on one 19th Century author who had no speciality or sources - and has been academically discredited. But fair game, & good enough to go to air with, if you're having a go at religion rather than science, yeah?


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SopranoAscends


Member

Posted Fri Jun 18th, 2010 12:17am Post subject: QI- It's wrong!

gjhsu said:
Or you could just say it's a simple matter of equalizing pressure. Whether being sucked or blown (er, behave...), it's a matter of perspective. In any case, it's one high-pressure volume moving to a low-pressure volume.

Sometimes it's just too hard to behave.

www.sopranoascending.wordpress.com

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