Poll

Which falls fastest a ton of bricks or a ton of feathers?

They fall at the same speed.
12 (48%)
A ton of bricks.
11 (44%)
A ton of feathers.
2 (8%)

Total Members Voted: 23

Voting closed: February 05, 2007, 02:50:50 AM

Simple IQ test.

• 24 Replies
• 4010 Views

midgard

• 1300
Simple IQ test.
« on: February 05, 2007, 02:50:50 AM »
You'll have to forgive me for posting a question that is highly ambiguous (made so because of poor definition and all the variables).

Still, I always like this as a simple IQ test.

I went with a ton of bricks.

Of course, because it's such an ambiguous question I figured there'd be a fair bit of room open for debate.

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joffenz

• The Elder Ones
• 1272
Simple IQ test.
« Reply #1 on: February 05, 2007, 03:04:00 AM »
Assuming they both start from the same height at a speed of zero, and the only force pulling them down is their weight, I would say a ton of bricks.

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Mugthulhu

• 11903
Simple IQ test.
« Reply #2 on: February 05, 2007, 03:05:19 AM »
a ton of bricks are just as heavy as a ton of feathers.

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joffenz

• The Elder Ones
• 1272
Simple IQ test.
« Reply #3 on: February 05, 2007, 03:13:40 AM »
True, but the question is asking which falls faster. Feather's have a much lesser density than bricks, so they will have a larger surface area. A large surface area means air resistance (friction) acting on the feathers will be greater. Thus, they fall slower.

beast

• 2997
Simple IQ test.
« Reply #4 on: February 05, 2007, 03:16:12 AM »
Obviously the answer is a tonne of bricks.

You could change the question around to this.

What falls faster - a tonne of feathers or one brick?

Physics says that all things fall at the same speed, regardless of their weight (well, the heavier weight is completely insignificant compared with the weight of the Earth if you want to be technical) - however clearly feathers have a great deal of wind resistance, and it doesn't matter how many you have, unless you've stuck them all together in a manner that they have an equal or less wind resistance than the bricks, they'll fall slower.

beast

• 2997
Simple IQ test.
« Reply #5 on: February 05, 2007, 03:17:41 AM »
Quote from: "cheesejoff"
True, but the question is asking which falls faster. Feather's have a much lesser density than bricks, so they will have a larger surface area. A large surface area means air resistance (friction) acting on the feathers will be greater. Thus, they fall slower.

Density doesn't really play much part.  What falls faster, a diamond or a block of pumas?  They both fall at the same speed.

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Mugthulhu

• 11903
Simple IQ test.
« Reply #6 on: February 05, 2007, 03:21:56 AM »
Quote from: "cheesejoff"
True, but the question is asking which falls faster. Feather's have a much lesser density than bricks, so they will have a larger surface area. A large surface area means air resistance (friction) acting on the feathers will be greater. Thus, they fall slower.

You're right, you got me.

EDIT:
Quote from: "beast"
Density doesn't really play much part.  What falls faster, a diamond or a block of pumas?  They both fall at the same speed.

Or maybe you didn't!  :shock:

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Beeper

• 364
Simple IQ test.
« Reply #7 on: February 05, 2007, 03:39:08 AM »
im with beast, and i think that pretty much destroys any debate
Easy as 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679

midgard

• 1300
Simple IQ test.
« Reply #8 on: February 05, 2007, 03:46:15 AM »
Quote from: "beast"
Density doesn't really play much part.  What falls faster, a diamond or a block of pumas?  They both fall at the same speed.

Okay, forgive me if this is going to come across as a simpleton's argument but I've used this page for the basis of my knowledge on my argument.

According to the link posted above:
• Everything that has a mass has gravity.
• The further you are away from the centre of the mass the less the gravity will affect you.
So suppose we drop a ton of brick and a ton of feathers on earth in a vacuum and measured it extremely accurately. If both the feathers and bricks were kept together as spheres and the bottoms of the spheres were lined up to an equal height would the bricks end up hitting the ground first?

If the bricks and feathers both have gravity as well as the earth and the bricks' massive centre is closer to the earth's than the feathers' then wouldn't the bricks gravity make the bricks win out in the end by the smallest fraction of a second even in a vacuum tube?

It's an honest question, I'm not trying to make a point just get an answer.[/list]

midgard

• 1300
Simple IQ test.
« Reply #9 on: February 05, 2007, 03:54:03 AM »
Can anybody think of other questions that are similar to this?

I'm basically looking for well known brain teasers that are actually wrong.

Also, I think that this question should be mandatory to answer before you're allowed onto the forum, what do you think?

beast

• 2997
Simple IQ test.
« Reply #10 on: February 05, 2007, 04:27:03 AM »
Regarding this new question:

"So suppose we drop a ton of brick and a ton of feathers on earth in a vacuum and measured it extremely accurately. If both the feathers and bricks were kept together as spheres and the bottoms of the spheres were lined up to an equal height would the bricks end up hitting the ground first?"

They would both hit the ground at the same time.

That is to say, there is no way that you could measure the very very slight difference between which hits the ground first

Consider the weight of the Earth -

5,974,200,000,000,000,000,000,000 kg - compared with two objects that weigh 1,000 kg - you can see that the possible slight difference between the objects, if we assume the density of the bricks is greater than the density of the feathers, which I'm not convinced would be the case anyway (I'm assuming you've compressed the feathers, so it's just a mass of feather - not feather and air).  Then there is no possible way that you could measure such a tiny difference. - We're talking about fractions of nano meters here.

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joffenz

• The Elder Ones
• 1272
Simple IQ test.
« Reply #11 on: February 05, 2007, 05:02:24 AM »
Quote from: "cheesejoff"
True, but the question is asking which falls faster. Feather's have a much lesser density than bricks, so they will have a larger surface area. A large surface area means air resistance (friction) acting on the feathers will be greater. Thus, they fall slower.

Quote from: "beast"
however clearly feathers have a great deal of wind resistance, and it doesn't matter how many you have, unless you've stuck them all together in a manner that they have an equal or less wind resistance than the bricks, they'll fall slower.

Er...I was saying the same thing as you.

Mass = density/volume, and since masses are equal, when density increases voume decreases.

Consider two parachutes made of the same material. They will have equal amounts of air resistance.

Now imagine you replace one with a far denser material that has the same weight. The parachute will be a lot smaller and thus has less air resistance.

midgard

• 1300
Simple IQ test.
« Reply #12 on: February 05, 2007, 05:58:44 AM »
Quote from: "beast"
Then there is no possible way that you could measure such a tiny difference. - We're talking about fractions of nano meters here.

So even if there is no possible to way to measure the difference would there be one?

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m4a1_assassin

• 71
Simple IQ test.
« Reply #13 on: February 05, 2007, 10:57:05 AM »
well, this is pretty subjective. i mean, are we to assume that where ever we drop these has an atmosphere? how dense are the feathers packaged?

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BOGWarrior89

• 3793
• We are as one.
Re: Simple IQ test.
« Reply #14 on: February 05, 2007, 12:42:57 PM »
Quote from: "midgard"
You'll have to forgive me for posting a question that is highly ambiguous (made so because of poor definition and all the variables).

Still, I always like this as a simple IQ test.

I went with a ton of bricks.

Of course, because it's such an ambiguous question I figured there'd be a fair bit of room open for debate.

Firstly, it's "faster", not "fastest"; only two objects are being compared, not more than two.

Secondly, congratulations on the creation of a "NEI" question; if we account for air resistance, the bricks fall faster.  If there is no air resistance (or if your physics book tells you that you can neglect it), they fall at the same speeds.

?

• Official Member
• 16983
Simple IQ test.
« Reply #15 on: February 05, 2007, 01:12:13 PM »
The original question is too ambiguous.  Specifying the height they're dropped from would help, assuming it's on Earth with our atmosphere (as opposed to a vacuum).  Drop them from a couple feet, I'm positive they fall at the same time.  Drop them from a couple miles, the feathers obviously hit wind resistance sooner.

But then again, I'm pretty sure that depends on their density and how they are packed together, and a ton of other factors.

In a vacuum, they fall at the same time, though.

8/30 NEVAR FORGET

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GeoGuy

Simple IQ test.
« Reply #16 on: February 05, 2007, 03:25:02 PM »
Naturally they both fall at the same speed in a vacuum. But I think you might have got the question wrong. The only version I've heard is "Which weighs more, a pound of gold or a pound of feathers?". In which case a pound of feathers weighs more because feathers are weighed using the Avoirdupois system, which has 16 ounces to a pound, and gold is weighed using the Troy system, which has 12 ounces to a pound.

But whatevs, the trick part of the question still works.

Dioptimus Drime

• 4531
• Meep.
Simple IQ test.
« Reply #17 on: February 05, 2007, 10:12:21 PM »
Quote from: "beast"
"So suppose we drop a ton of brick and a ton of feathers on earth in a vacuum and measured it extremely accurately. If both the feathers and bricks were kept together as spheres and the bottoms of the spheres were lined up to an equal height would the bricks end up hitting the ground first?"

Realizing that it's just a hypothetical situation, but still it'd basically be impossible to be able to acheive a vacuum and still have gravity affect an object. Also, wouldn't the shape not make a difference if it were in a vacuum?

~D-Draw

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• Official Member
• 16983
Simple IQ test.
« Reply #18 on: February 05, 2007, 10:21:18 PM »
Quote from: "DiegoDraw"
Realizing that it's just a hypothetical situation, but still it'd basically be impossible to be able to acheive a vacuum and still have gravity affect an object.

What the crap are you talking about?  The moon has no atmosphere, haven't you seen the feather and hammer "experiment" they did out there?

Quote from: "DiegoDraw"
Also, wouldn't the shape not make a difference if it were in a vacuum?

No, but dimension would be useful for empirical purposes.  You know, to make sure they fall exactly the same way and everything.

8/30 NEVAR FORGET

skeptical scientist

• 1285
• -2 Flamebait
Simple IQ test.
« Reply #19 on: February 05, 2007, 11:24:48 PM »
Quote from: "DiegoDraw"
Quote from: "beast"
"So suppose we drop a ton of brick and a ton of feathers on earth in a vacuum and measured it extremely accurately. If both the feathers and bricks were kept together as spheres and the bottoms of the spheres were lined up to an equal height would the bricks end up hitting the ground first?"

Realizing that it's just a hypothetical situation, but still it'd basically be impossible to be able to acheive a vacuum and still have gravity affect an object. Also, wouldn't the shape not make a difference if it were in a vacuum?

~D-Draw

Actually, assuming the sphere of feathers was larger, it would take slightly longer to hit the ground, as its center of mass would be slightly higher, so the average force on its constituent feathers would be slightly less. As Beast indicated, this effect is probably on the order of nanoseconds, if not much smaller, but it is there.

But for all intents and purposes, if you are actually performing the experiment, you aren't in a vacuum, so the ton of bricks will hit the ground significantly sooner.
-David
E pur si muove!

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BOGWarrior89

• 3793
• We are as one.
Simple IQ test.
« Reply #20 on: February 05, 2007, 11:37:53 PM »
I was going to say the feathers, but then the right answer hit me like a ton of bricks.

beast

• 2997
Simple IQ test.
« Reply #21 on: February 06, 2007, 12:28:56 AM »
Quote from: "DiegoDraw"

Realizing that it's just a hypothetical situation, but still it'd basically be impossible to be able to acheive a vacuum and still have gravity affect an object. Also, wouldn't the shape not make a difference if it were in a vacuum?

~D-Draw

Oh lol.

Not sure if you're aware, but gravity has the exact same effect in a vacuum as outside of it.  Most objects in space are in vacuums.  Space is a essentially a vacuum and there is still a serious gravitational effect.  Vacuums have nothing to do with "zero gravity."  The reason you are weightless in space is not because you're in a vacuum but because you're centrifugal forces are equal to the pull of gravity (so you move around the planet instead of falling or being slung away).  Essentially the resultant vector of the two forces is sideways.

Regarding the shape in a vacuum, it's not the shape that makes a difference but the density.  As I stated, in objects that are so small (compared with the other object attracting them) - it doesn't make any significant difference.  However if we were talking about the gravitational effects of two planet sized objects - denisty would play a significant part.

Leg me give you an example.  You have a planet the size of the Earth and two objects that are the same size as the earth.  Knowing their mass and size you can easily calculate the force of attraction between the two objects (also knowing how far away they are from each other).  Now imagnie that one is made of solid gold, and the other is a black hole.  Which has a greater force of attraction?  Obviously this hypothetical question is physically hard to reproduce in real life but I'm sure you can see how important density is.

The formula for measuring the force of gravity is:

force = [Gravitational constant x mass(object1) x mass(object 2)]/{distance between the two objects.}^2

If you want to experiment with that - try putting in some numbers, and then changing the mass of one of those objects without changing the distance between them - that's the same as changing the denisty.  You can see that the higher the mass, the higher the the force.  Also note that if you decrease the distance between the two objects the force is also bigger (another way of calculating a change in density).

skeptical scientist

• 1285
• -2 Flamebait
Simple IQ test.
« Reply #22 on: February 06, 2007, 01:14:46 AM »
Quote from: "beast"
The formula for measuring the force of gravity is:

force = [Gravitational constant x mass(object1) x mass(object 2)]/{distance between the two objects.}^2

If you want to experiment with that - try putting in some numbers, and then changing the mass of one of those objects without changing the distance between them - that's the same as changing the denisty.  You can see that the higher the mass, the higher the the force.  Also note that if you decrease the distance between the two objects the force is also bigger (another way of calculating a change in density).

Yeah, but f=ma, so the force on an object being proportional to the mass is the same as saying that the acceleration is independent of mass, and therefore density. Since "falling faster" depends only on acceleration, they would be the same.
-David
E pur si muove!

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Tigerfan29

• 15
falls faster
« Reply #23 on: February 07, 2007, 06:14:14 PM »
Are theytied up in a bag or losely falling. in a bag it would be feathers because of less surface area since you can fit more in a smaller bag. out of a bucket it would be bricks because feathers are more wind resistand.
rtifical inteligence is no match for natural stupidity.
-me

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Tigerfan29

• 15
Falls faster
« Reply #24 on: February 07, 2007, 06:27:17 PM »
sorry I was late
Could they be broken and put into bags to have less air in the bag
rtifical inteligence is no match for natural stupidity.
-me