Riddle confusion

[AniJan]

This riddle has been confusing me for a bit.

I'm stupid, so I can't figure it out. 

"There is a bridge that can hold exactly 1000 tons. If something that weighs over 1000 tons, the bridge will collapse. It can hold something if it weigh exactly 1000 tons. A truck weighing exactly 1000 tons crosses the bridge. Halfway across, a bird lands on it. Does the bridge collapse?

Yes or no and why?"

 

I know the answer is no, but I can't find reasoning..

[rhyseyness]

"It'll probably be fine"

-engineering proverb

[Dylanc1500]

Because mostly only half the weight of the truck is supported by the bridge, the other half would not yet be on the bridge. To support your answer of no.

 

However, the out come of this "riddle" is dependent on the length of the truck and what "halfway across" is. Halfway across could mean the full weight of the truck is supported by the bridge, or that it isn't fully supported by the bridge.

[TidaLWaveZ]

The riddle is missing the length of the bridge, that's why it's confusing.

 

It should note that the bridge is fairly long making it so that by the time the truck is halfway across the bridge it has burned enough gasoline to offset the birds weight.

[dalekphalm]

Assuming that the bridge can hold EXACTLY 1000 tons and no more, and that the truck is entirely on the bridge, and weighed exactly 1000 tons, then yes, a bird landing on the truck would cause it collapse.

 

But that's not a good riddle, since there are many variables the riddle doesn't give that would affect the outcome in a real world scenario.

[AniJan]

3 hours ago, dalekphalm said:

Assuming that the bridge can hold EXACTLY 1000 tons and no more, and that the truck is entirely on the bridge, and weighed exactly 1000 tons, then yes, a bird landing on the truck would cause it collapse.

 

But that's not a good riddle, since there are many variables the riddle doesn't give that would affect the outcome in a real world scenario.

 

9 hours ago, TidaLWaveZ said:

The riddle is missing the length of the bridge, that's why it's confusing.

 

It should note that the bridge is fairly long making it so that by the time the truck is halfway across the bridge it has burned enough gasoline to offset the birds weight.

 

9 hours ago, Dylanc1500 said:

Because mostly only half the weight of the truck is supported by the bridge, the other half would not yet be on the bridge. To support your answer of no.

 

However, the out come of this "riddle" is dependent on the length of the truck and what "halfway across" is. Halfway across could mean the full weight of the truck is supported by the bridge, or that it isn't fully supported by the bridge.

I had just learned the answer from the guy who created it:

As the truck crosses the bridge, the fuel slowly descends, meaning that weight also decreases.

 

 

It's stupid, lol.

[yathis]

13 hours ago, AniJan said:

There is a bridge that can hold exactly 1000 tons. If something that weighs over 1000 tons, the bridge will collapse. It can hold something if it weigh exactly 1000 tons. A truck weighing exactly 1000 tons crosses the bridge. Halfway across, a bird lands on it. Does the bridge collapse?

Yes or no and why?"

Yes it collapses because it weighs 1000 tons plus extra weight so it weighs more then 1000 tons.

1000 tons = 9.07185e+8 grams so that is 9 071 850 000 00 which is 90, 718 500 000 grams or 90 billion 718 million 500 thousand grams

add the bird to the equation and now it weighs 90,718,500,010 grams or 10 grams more then 1000 tons. So yes it would collapse.

 

BTW the original postulated question states nothing about a running truck. It could be downhill and the truck is off and in neutrel. But going by your logic then you'd have to add the weight of the driver as we go back to the stated question which is very flaky question to ask.

[samiscool51]

14 hours ago, rhyseyness said:

"It'll probably be fine"

-engineering proverb

anyways, sometimes you have to riddles litery

bridges are designed to support about 0.5x more than their intended max weight to ensure they don't collapse

[yathis]

What is the error rate of the weighing mechanism?

Is it real sensitive that even a leaf falls on it and the bridge collapses, or does it need to be 100lbs or whatever.

 

You need to have more specifics in your question is what I am saying.

[Tsuki]

i think the real question here is whether its an african swallow or a european one.

[Kamina]

Bird's bones are hollow.

Birds are also too stupid to land on moving vehicles. 

 

[Dash Lambda]

13 hours ago, AniJan said:

I had just learned the answer from the guy who created it:

As the truck crosses the bridge, the fuel slowly descends, meaning that weight also decreases.

And the riddle says "a truck weighing exactly 1000 tons."

The way the riddle is written, is presents a truck with constant weight.

So they guy who wrote it isn't very good at riddles.

[Real_PhillBert]

Nope. Bridges are built with a >0 safety factor.

[dalekphalm]

20 hours ago, AniJan said:

 

 

I had just learned the answer from the guy who created it:

As the truck crosses the bridge, the fuel slowly descends, meaning that weight also decreases.

 

 

It's stupid, lol.

Well that depends on fuel consumption rate, the weight of fuel per unit of measurement, compared to the weight of a bird.

 

The type of bird was not specified.

 

If an Eagle or other large bird of prey lands on that truck, the weight of the bird will counteract and overcompensate for the weight of lost fuel due to combustion.

 

Thus, the bridge will still collapse.

 

Take for example, a female Golden Eagle, which can be found in the Continental US. They on average weigh 5.1kg - that's 11.2 lbs for the yanks. 11.2 lbs is a lot. Gasoline weighs just over 6 lbs per US Gallon.

 

So now we'd need to know fuel capacity and of course MPG rating of the truck. But I'd be extremely skeptical that the truck would consume more than 2 gallons of fuel by simply driving over a bridge.

 

A quick Google search online shows one example of a Dump Truck (a rather large and heavy truck) consuming just over 5 MPG. Unless the bridge was extremely long, the truck would use considerably less than a gallon of fuel crossing, and thus, the weight of a female Eagle would cause the truck to exceed the weight limit, even with consumed fuel taken into consideration.

 

TL;DR, this riddle is goddamn stupid.

[Dash Lambda]

19 minutes ago, dalekphalm said:

-snip-

Oh-ho, if we're gonna talk about the numbers, I present to you this:

Spoiler

The BelAZ 75710, the largest dump truck in the world, weighing in at just under 400 tons.

[dalekphalm]

19 hours ago, Dash Lambda said:

Oh-ho, if we're gonna talk about the numbers, I present to you this:

  Reveal hidden contents

The BelAZ 75710, the largest dump truck in the world, weighing in at just under 400 tons.

True - but the entire premise of this "riddle" is utterly ridiculous. A 1000 ton truck?

 

The idea that a 1000 ton truck could even fit on a bridge to begin with is absurd.

 

I give you, the Bagger 288:

Spoiler

https://en.wikipedia.org/wiki/Bagger_288

 

Weighing in at roughly 13,500 tons.

 

Sure, it's a bit more than 1000, but it's to give a sense of scale.

 

I actually can't find a "truck" that weighs 1000 tons at all. I did find several dump trucks that weighed in the low 100's of tons (The biggest was around 650 tons with full load).

 

And frankly, I question whether any of those trucks could reasonably fit onto a bridge.

[Godlygamer23]

The riddle loses its point when its basic premise is being questioned. The riddle has holes in it, and if the person states that the vehicle is constantly losing fuel(as it would be in a real world scenario), then the truck's weight would not be a constant, but would be a variable since it is always changing with the fuel burning, and therefore shouldn't be defined as a vehicle that weighs EXACTLY 1,000 tons.

[dalekphalm]

1 minute ago, Godlygamer23 said:

The riddle loses its point when its basic premise is being questioned. The riddle has holes in it, and if the person states that the vehicle is constantly losing fuel(as it would be in a real world scenario), then the truck's weight would not be a constant, but would be a variable since it is always changing with the fuel burning, and therefore shouldn't be defined as a vehicle that weighs EXACTLY 1,000 tons.

Agreed, the wording of the riddle, using the term "exactly 1000 tons", contradicts the given answer:

 

"Oh, you know how I said it weighed exactly 1000 tons? I lied. The fuel burns and the weight is variable. HAHA!"

 

It's like a 10 year old thought up the riddle, then got pissed when the flaws were called out, so he changed the answer to spite the person so they would still get the answer wrong.

[Godlygamer23]

Just now, dalekphalm said:

Agreed, the wording of the riddle, using the term "exactly 1000 tons", contradicts the given answer:

 

"Oh, you know how I said it weighed exactly 1000 tons? I lied. The fuel burns and the weight is variable. HAHA!"

 

It's like a 10 year old thought up the riddle, then got pissed when the flaws were called out, so he changed the answer to spite the person so they would still get the answer wrong.

I'm not sure if bringing weight distribution into this would be a wise decision either, since that might also affect the answer. 

[dalekphalm]

Just now, Godlygamer23 said:

I'm not sure if bringing weight distribution into this would be a wise decision either, since that might also affect the answer. 

it certainly could affect the answer, since the weight exhibited by each contact point (the wheels) with the bridge might be different.

 

Also, if the payload of the truck itself (assuming it's a dump truck or other cargo carrier) shifted in transit across the bridge, the acceleration of the payload and the kinetic energy could increase the effective weight momentarily, which may or may not be enough to cause the bridge to fail.

[Dash Lambda]

58 minutes ago, dalekphalm said:

I actually can't find a "truck" that weighs 1000 tons at all. I did find several dump trucks that weighed in the low 100's of tons (The biggest was around 650 tons with full load).

This thing, a Flower-Class corvette, is about 1000 tons:

Spoiler

So yeah, I can't imagine there's a truck that heavy.

 

1 hour ago, dalekphalm said:

And frankly, I question whether any of those trucks could reasonably fit onto a bridge.

A typical bridge, or at least for large bridges, seems to support 4 lanes, which is wide enough for the BelAZ.

[dalekphalm]

32 minutes ago, Dash Lambda said:

This thing, a Flower-Class corvette, is about 1000 tons:

  Hide contents

So yeah, I can't imagine there's a truck that heavy.

 

A typical bridge, or at least for large bridges, seems to support 4 lanes, which is wide enough for the BelAZ.

Wide enough if all four lanes were unobstructed, like a typical downtown road in a bigger city. But you also have to consider that most 4-lane bridges, especially the longer and bigger variety, generally have some sort of divider in the middle - whether a simple concrete one, or a larger, spaced out divider that acts as part of the main support mechanisms.

 

Also consider that the average weight of a car is 1.85 tons. So a bridge that can handle a 1000 ton weight would be able to fit 540 cars on it. I doubt even a longer bridge can hold more than 100 cars all at once in the space provided - they might be able to take the weight, but I don't think there's enough physical space, unless you start stacking the cars on top of one another - and at that point, all practicality becomes moot, and you're entirely in the realms of hypothetical non-realistic fiction.

[Dash Lambda]

58 minutes ago, dalekphalm said:

Wide enough if all four lanes were unobstructed, like a typical downtown road in a bigger city. But you also have to consider that most 4-lane bridges, especially the longer and bigger variety, generally have some sort of divider in the middle - whether a simple concrete one, or a larger, spaced out divider that acts as part of the main support mechanisms.

Not all of them, so it's not unreasonable to propose a hypothetical four-lane bridge without obstructions.

 

59 minutes ago, dalekphalm said:

Also consider that the average weight of a car is 1.85 tons. So a bridge that can handle a 1000 ton weight would be able to fit 540 cars on it. I doubt even a longer bridge can hold more than 100 cars all at once in the space provided - they might be able to take the weight, but I don't think there's enough physical space, unless you start stacking the cars on top of one another - and at that point, all practicality becomes moot, and you're entirely in the realms of hypothetical non-realistic fiction.

There are of course multi-level bridges, but they're not really meaningful for this...

Even if a bridge can support 1000 tons of cars across its length, though, that means nothing about a point load. Having 1000 tons on top of a single support pillar on a bridge that's built to break at 1000 tons total is just certain failure.

[yathis]

You'd have to know how much fuel it uses as it drives over the bridge, plus you'd have to know where it started, the slope, the wind, the elevation, and the exact gravitational pull it has because if I am not mistaken there are different area's in the world where that # is different. Also the elevation would be air/fuel mixture. Also how much dirt and dust is on the bridge? Insects? Wind Direction? Rain?