Would the boat sink?

[Canai]

I think he's talking about a huuuuuge screen mesh cage of some sort, not a little box. Now, if they were in a box and all facing the same way, if you put a tube at the back of the cage and made the cage a kind of long tube (redundant yes I know it is) would you be able to make a hummingbird powered jet engine?

 

[BrianH1]

was i drunk at the time of putting the hummingbirds in the box?

 

[FoBoT]

i think PETA will want to know about your evil plot to enslave these hummingbirds

 

[Xyo II]

Originally posted by: ahurtt

Originally posted by: illusion88
the floating objects aren't exerting any force on the boat. Infact, they are pulling the boat out of the water with the force of their gravity!! (mathmatically insignificant though).

Ok how about this. . .If you have an aquarium with 20 gallons of water in it, and then you put in a 2 pound fish, assuming the fish is alive and floats suspended in the water, not touching any sides, does the aquarium now weigh 2 pounds more?

You are terrible at the "let's make up a hypothetical situation where two forces could or could not negate the purpose and/or effect of the other, resulting in which a situation does or does not happen but can lead to lengthy hypothetical discussion about said scenario" game. :laugh:

 

[illusion88]

Originally posted by: ahurtt

Originally posted by: illusion88
the floating objects aren't exerting any force on the boat. Infact, they are pulling the boat out of the water with the force of their gravity!! (mathmatically insignificant though).

Ok how about this. . .If you have an aquarium with 20 gallons of water in it, and then you put in a 2 pound fish, assuming the fish is alive and floats suspended in the water, not touching any sides, does the aquarium now weigh 2 pounds more?

Absolutly! You are adding to the water, increasing downward force towards the scale below the aquarium.

Even if the box was air tight, and you had 100000000000 objects floating inside it, they wouldn't effect the weight of the boat at all. All it's going to do, is displace the air around the objects.

I use floating objects in the example so people can stop talking about the downward force from their wings.

 

[glugglug]

The air movement from the birds flapping their wings creates a pressure differential between the top and bottom of the container, and this pressure differential carries a force exactly equal to the weight of the birds pushing the boat downwards.

So it sinks.

P.S, during liftoff, the downward force exterted on the air by the birds (and transferred to the boat) exceeds their weight.

 

[ElFenix]

Originally posted by: FoBoT
so you know how many hummingbirds it would take to make 91 pounds?!? :Q

that is BULK HUMMINGBIRDS!

hummingbirds weigh about 3-4 grams

that is about 12,000 hummingbirds!!

are those alternator sized hummingbirds?

 

[Zolty]

humming bird in flight does not add weight to the container.

 

[swtethan]

yes, hummingbirds have to land sometime

 

[fleshconsumed]

mugs gave the right answer. It depends on the box. First of all if the box was small enough and airtight the hummingbirds wouldn't be able to fly at all. Even supposing if the box is big enough, but airtight (or with very minimal air ventilation holes) the downward pressure from the winds would exert a 91 pound pressure on the bottom of the box so it would be the same as if the box weighed 91+10 pounds.

A better way of thinking about it is ask yourself, would an eagle be able to deliver a box parcel (say 8x8x8 feet) if he was inside of it? No because the wind pressure from his wings flapping would exert the same pressure on the bottom of the box as the force that required him to take off. Both will cancel out.


The only way it could work if the box was really a cage, i.e. almost fully open.



PS these questions airplane/chopper/hummingbirds are really really stupid, even a 9th grader with basic physics knowledge could answer these.

 

[Canai]

Originally posted by: illusion88

Originally posted by: ahurtt

Originally posted by: illusion88
the floating objects aren't exerting any force on the boat. Infact, they are pulling the boat out of the water with the force of their gravity!! (mathmatically insignificant though).

Ok how about this. . .If you have an aquarium with 20 gallons of water in it, and then you put in a 2 pound fish, assuming the fish is alive and floats suspended in the water, not touching any sides, does the aquarium now weigh 2 pounds more?

Absolutly! You are adding to the water, increasing downward force towards the scale below the aquarium.

Even if the box was air tight, and you had 100000000000 objects floating inside it, they wouldn't effect the weight of the boat at all. All it's going to do, is displace the air around the objects.

I use floating objects in the example so people can stop talking about the downward force from their wings.

but the hummingbirds are not floating... ?

 

[Aharami]

Originally posted by: Ramma2
If a hummingbird hovers above a scale, does it register on the scale?

Nope.

Does the boat sink?

Nope.

Is this lame?

Yep.

/thread

 

[fleshconsumed]

Originally posted by: Ramma2
If a hummingbird hovers above a scale, does it register on the scale?

Yes.

Does the boat sink?

Yes.

Is this lame?

Yep.

 

[Canai]

Originally posted by: fleshconsumed

Originally posted by: Ramma2
If a hummingbird hovers above a scale, does it register on the scale?

Yes.

Does the boat sink?

Yes.

Is this lame?

Yep.

/thread

 

[silverpig]

Think about watching a helicopter land in a field of long grass. The wind from the rotors required to hold up the helicopter definitely exerts a downwards force on the ground.

It'd be a very complex aerodynamic problem, and while I'm sure that not all 91 lbs would be exerted directly on the bottom of the box, there would be some downward force.

 

[FoBoT]

what if the air in the box is 10% helium?

 

[Canai]

then the birds would have to pump their wings even harder, generating more force. either that or fall to the bottom of the box.

of course, if the air were to be any different than normal air, the box would have to be sealed.

 

[randay]

The boat takes off normally. The only difference is that the hummingbirds have to flap thier wings twice as fast.

 

[Fern]

Originally posted by: ahurtt
....... There are a couple of tiny airholes in the top but other than that the container is solid. If you put the container on the boat but all the hummingbirds inside it were hovering in the air (not standing around on the bottom of the container) would it sink the boat?

It'll sink.

If the walls of the box were mesh, it may float.

Fern

 

[hiredgoons]

Originally posted by: Canai
then the birds would have to pump their wings even harder, generating more force. either that or fall to the bottom of the box.

of course, if the air were to be any different than normal air, the box would have to be sealed.

If it were 10% Helium by mass, the birds would just displace more of it. If it were 10% as a mole fraction, then yes they would have to flap harder.

 

[FoBoT]

moles can't fly, they don't even have wings!

 

[Canai]

maybe the box contains half moles and half hummingbirds?

or maybe half a mole of hummingbirds even?

 

[DarkKnight69]

Originally posted by: ahurtt

Originally posted by: illusion88
the floating objects aren't exerting any force on the boat. Infact, they are pulling the boat out of the water with the force of their gravity!! (mathmatically insignificant though).

Ok how about this. . .If you have an aquarium with 20 gallons of water in it, and then you put in a 2 pound fish, assuming the fish is alive and floats suspended in the water, not touching any sides, does the aquarium now weigh 2 pounds more?

THe problem with this is that water weighs more then air, we are not weighing the air in this scenario. If you weighed a tank in water with water in it, would have the same effect.

 

[hiredgoons]

I'd like to see a 10 lb box that can hold half a mole of hummingbirds

 

[hiredgoons]

Originally posted by: DarkKnight69

Originally posted by: ahurtt

Originally posted by: illusion88
the floating objects aren't exerting any force on the boat. Infact, they are pulling the boat out of the water with the force of their gravity!! (mathmatically insignificant though).

Ok how about this. . .If you have an aquarium with 20 gallons of water in it, and then you put in a 2 pound fish, assuming the fish is alive and floats suspended in the water, not touching any sides, does the aquarium now weigh 2 pounds more?

THe problem with this is that water weighs more then air, we are not weighing the air in this scenario. If you weighed a tank in water with water in it, would have the same effect.

It's the same idea though - the fish displace the water and add to the weight; the hummingbirds displace the air and (assuming it isn't a cage and the air doesn't all go somewhere else) add to the weight of the box.