Fish Quiz

Good one Matt!

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This is the old “would you rather have 10 pounds of bricks or 10lbs of feathers fall on your head”, answer, it doesnt matter.

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I’ll take the 10 pounds of feathers….it may weight the same, but it wont cut your head up

Rereading you post, maybe I need to explain more.

A hovering helicopter still weighs, it is in air, not water.

If the fish is floating, it is because of several factors. It WEIGHS 10lbs. Since fish and most living things are neutral bouyant, for it to float, it has to be because there is gas somewhere in its system. That air was in its system when it was out of the water, that air as weight(positive or negative) AND area. So for the fish to float, it has gas in it, the area of that gas is disipating more water than a fish with no gas in it. The total weight is not different.

The “neutral buoyant” arguement carries no merit.

Water is neutral buoyant, if you add more water, will it weigh more?

Ok, I am done unless someone claims that I am wrong.

I was hoping this would happen. Dave I follow your reasoning and intuition but it still weighs 100# exactly.
I’m 100% sure on this. Usually when I give the “hanging the rock in the water by string”, people understand it better.

The northern isnt hanging from a string. It is in the water with nothing altering or removing the 10lb of weight that it represents.

I have nothing against you personally, but you are 100% wrong. I would say 110%, but that would not be good math or science.

Is it really the same as the rock on a string though? The rocks weight is being transfered to whatever it’s hanging from. With the fish, it’s weight is being transferred to the water through displacement isn’t it? Of course, what do I know, I tried the experiment with a cat.

I feel like I may need to go talk to one of my professors to get the answer for this. Although it is fun watching the bantering going back and forth

I’ll talk to a professor here and see what he says about it, and then i’ll let you know. But please keep up the amusing discussions at least until I can talk to a prof about it.

no problem….The string in the string scenario is replaced by the fish’s air bladder. Both have the same effect in keeping the rock and fish elvated. This Was a physics problem from my freshmen year in highschool. One I’ll never forget. But once its on paper, it becomes obvious.I’m not fully accredited but I’m a 4th year engineering student at SCSU. If that counts for anything.

Hey, no offense taken, like I said its difficult to picture at first.

If you put a boat in 100,000lbs like you said, only the part of the boat above water would show up on the scale.

May be a stupid question, but here goes. How do they weight fish at a tournament? I thought it was in a bucket of water, or a bag? My head hurts!

The truth is that it doesnt matter what you put in the water whether it be fish, lead, rock, ice, more water, jello, oil, etc. Whatever it weights, unless these is a phyical reaction, will add to the weight.

Think of it this way-take a 10 gallon fish tank. Pack it with fish to the top, add 1 gallon of water, does it just weight the same as one gallon of water? If so, then you have a billion dollar idea for transporting fish.

the air in the bladder just displaces that much more water. It would need to make the fish lighter than air to not contribute to the weight-NOT lighter than water.

Matt,

If you have access to a scanner, maybe you should write out the problem and then scan it into the computer. Then post it up here and maybe it will be easier to see. Just a thought

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If you have One hundred pounds of water counting the weight of the container on a scale reading 100lbs, and you drop a live 10 lb northern into it, What does the scale read?

Theres actually an answer to this one.

If you’ve heard this before stay quiet. I want to hear the theories.

First one to get it right with the proper explanation gets a big ego.

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I think your asking the wrong question Matt… the actual “bit” goes something like this…

If 1 gallon of water weights 8.34 lbs would adding a 2 lb fish to the water change the weight of the water?

Most of the time the answer would be “No”.

If the water was in a bucket, and a 2 lb fish is added to it, the contents of the bucket would then be 8.34 lbs + 2 lbs = 10.34 lbs. BUT — the water would weigh the same: 8.34 lbs. No water would have been gained or lost because of the presence of the fish. (There’s the ‘ha-ha’ of the bit — water weighs the same 8.34 lbs.)

But since we’re all discussing water displacement, the answer is different if bucket had initially been filled to the brim. In that event, adding the fish obviously would cause the bucket to overflow. Thus the water would weigh 2 pounds less: 6.34 pounds in the case where you could exactly slide the fish in and displace only the volume of water equal to the fish. The density of a two pound fish is the same as the density of the water. Fish can swim and hover in the water because, using their internal air bladders, they control their buoyancy to be neutral. That’s why they neither sink nor float. So they weigh the same as the water they displace, thus leaving the mass of the contents of the bucket unchanged in that special case.

There is no other answer to this question.

So I was the first to respond correctly to the question? AND I had two correct answers? Man I can feel my ego growing as I think…you guys need to stop this PLEASE! Really though, I would like to know the true answer to the riddle by someone that is certified to answer it and 100% sure…..not saying either of you aren’t so please don’t take it that way but one of you isn’t Some more to think about though: because of the different density, oil and water separate when added together but still weigh the same as their combined weight right? Also, when they do a body mass index in a giant pool of water (you know, the test that measures your body fat) shouldn’t the fat add weight to the measurement too? Now I’m really confused Please help

110 lbs.

Gianni
Technical Director
Super-Cool Company

Here’s another one:

If you take a gallon of Ethanol and add a gallon of water, the Eth will absorb (chemically combine with) a portion of the water, giving you a combined volume less than 2 gallons.

Will the combined volume of liquid weigh differently from it’s component parts?

Only if gas or another substance is released or created by the reaction.

This isn’t that tough.

If you add something to a half-filled bucket, the water it displaces will stay in the bucket and the bucket will get heavier. The reading on the scale will increase.

However, if you add a fish to a full bucket of water, the water it displaces will leave the bucket. Since a fish has the same density of water, the fish will have the same weight as the water it displaces. Therefore the reading of the scale will not change.

End story. No rocks on strings, no helicopters hovering, just basic physics. It’s called Archimedes’s Principle. It says that the buoyant force on the object is equal to the weight of the displaced fluid.

Thus, the weight of water displaced is equal to the weight loss of the object. As both water and the fish have a density of 1.00 gm/cm3, if you drop a 10 lb fish (or any other 1.00 gm/cm3 item (such as more water) in a 100lb bucket of water that is filled to the brim, the water displaced by what you added and the weight stays the same.

However, if the bucket is not full and can accomodate the 10lb fish without displacing water outside of the bucket the overall weight will be 110 lbs.

then there was my physics prof that used to ask for proof, via Archimedes principal, that a cast iron bathtub would float down the Mississippi.

dave

There is still 10 lbs of gravity pulling down on the fish, so 100 + 10 = 110 lbs. If you add a 10 lb. water balloon to the tank both = 110 lbs. Same thing.

So if you have a bottle that can only hold 5 gallons and another bottle that can only hold 3 gallons nothing more. you have an unlimmited amount of water. how do you get EXACTLY 4 gallons into the 5 gallon bottle?

You have ten bags of coins with 25 coins in each bag. Genuine coins weigh 5 grams, but one of the bags contains counterfeit coins which each weigh 1 gram less than genuine coins. You have a scale, but are permitted to use it only once. How do you determine which bag has the counterfeit coins?

One more for all you guys that like to split things down to the penny.

Three men stop at a hotel during a road trip and are told by the desk clerk there is only one room left, and that it would cost $30 for the night. They each pay the clerk $10 and go to the room. The desk then realizes that he has overcharged them by $5. He then send the bellboy to the room with $5 to return to the men. The bellboy, not being very honest, figures that since you can’t evenly split $5 3 ways, he’ll keep $2 and give the 3 men $1 each.

So, the room cost each man $9, for a total of $27, plus the $2 the bellboy kept, for a total of $29. Where did the missing $1 go?

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So if you have a bottle that can only hold 5 gallons and another bottle that can only hold 3 gallons nothing more. you have an unlimmited amount of water. how do you get EXACTLY 4 gallons into the 5 gallon bottle?

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Step 1: Fill up the 5 gallon bucket
Step 2: Fill the 3 gallon using water from the 5 gallon. There’s now 3 gallons in the 3 gallon and 2 in the 5 gallon
Step 3: Dump out the three gallon bucket
Step 4: Now dump the 2 gallons from the 5 gallon bucket into the 3 gallon container.
Step 5: Fill up the 5 gallon bucket again
Step 6: Fill the 3 gallon bucket the rest of the way with water from the 5 gallon. There’s now 3 gallons in the 3 gallon bucket and 4 gallons in the 5 gallon bucket.

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Step 1: Fill up the 5 gallon bucket
Step 2: Fill the 3 gallon using water from the 5 gallon. There’s now 3 gallons in the 3 gallon and 2 in the 5 gallon
Step 3: Dump out the three gallon bucket
Step 4: Now dump the 2 gallons from the 5 gallon bucket into the 3 gallon container.
Step 5: Fill up the 5 gallon bucket again
Step 6: Fill the 3 gallon bucket the rest of the way with water from the 5 gallon. There’s now 3 gallons in the 3 gallon bucket and 4 gallons in the 5 gallon bucket.

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Nice a little different then my way, I think.

Fill the three gallon bottle. Pour its contents into the five gallon bottle. Refill the three gallon bottle. Pour as much of its contents into the five gallon bottle as will fit, meaning two gallons. That leaves one gallon in the three gallon bottle.

Dump out the five gallon bottle. Pour the one gallon of water remaining in the three gallon bottle into the five gallon bottle. Fill the three gallon bottle and pour it into the five gallon bottle. It will now have four gallons in it.

the room cost 25 dollars, plus the 2 dollars the bellhop kept for a total of 27, not 29. You added the bellhops money twice to the 25 dollar room to make it sound like there is a missing dollar.

25 dollars is in the till + 3 dollars back + 2 dollars in the theif’s pocket = 30 dollars.

I saw that water bottle riddle in Die Hard 3.

I tried Gianni’s experiment with the ETOH and water and then drank it. I think the Gov’t is spying on me cuz I can see the invisible black helicopters hovering in my backyard and there’s a 10# northern in my birdbath. Shhhhhh… be careful what you say. The squirrels have ears.

You didn’t drink it without your tinfoil hat on, did you?

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You have ten bags of coins with 25 coins in each bag. Genuine coins weigh 5 grams, but one of the bags contains counterfeit coins which each weigh 1 gram less than genuine coins. You have a scale, but are permitted to use it only once. How do you determine which bag has the counterfeit coins?

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Too tuff?