Helicopter in box

[BornReady]

Siphorous' plane on a conveyor belt reminded me of the helicopter in a box. You guys probably won't fall for this one since you were too smart for the first one. But here it goes.

Imagine a large closed box sitting on top of a weight scale. A helicopter is sitting on the floor inside the box. After the helicopter takes off will the weight on the scale decrease?

 

[HK]

I'm really, really bad at these puzzles.

I think yes, because the helicopter is no longer helping the box press down on the scales.

 

[Zorak]

No, because to displace the helicopters own weight, and gain lift, it would have to exert a downward force equal to its weight.

 

[Guyzerr]

No, because to displace the helicopters own weight, and gain lift, it would have to exert a downward force equal to its weight.

Wouldn't it have to exert a force more than it's weight? If it just equaled it's weight it wouldn't lift off. It really isn't the downward force of the wind that lifts the thing off the ground anyway. It's the lift generated from the top of the blades. Same as an aircraft wing. Without lift it won't go up.

 

[BornReady]

It really isn't the downward force of the wind that lifts the thing off the ground anyway. It's the lift generated from the top of the blades. Same as an aircraft wing. Without lift it won't go up.

Ah, the great Newton vs. Bernoulli debate. Regardless of which theory you prefer, I think we can all agree the rotors force air downward. The force of that air against the floor of the box will create a weight equal to that of the helicopter assuming it is hovering at a constant height.

 

[Guyzerr]

Ah, the great Newton vs. Bernoulli debate. Regardless of which theory you prefer, I think we can all agree the rotors force air downward. The force of that air against the floor of the box will create a weight equal to that of the helicopter assuming it is hovering at a constant height.

Ok so lets say a chopper that weighs 5000 lbs is hovering 20' off the ground and a human that weighs 200 lbs walks under it ( which happens all the time ) why doesn't he get blown off the planet if the downward force of the air is at least 5000 lbs? I'm not an aeronautical engineer but when I think of your theory it doesn't make sense. Maybe you can explain it to me.

 

[BornReady]

It's because the force is spread out over a large area. Say the rotor is 20' tip to tip. Then the area under the rotors spin is 314 square feet. Spread the 5000 lb force over that area and it's only about 0.1 psi. Not much really.

 

[Guyzerr]

I'm still not buying the box thing but I am interested enough to do some research on it.

 

[BornReady]

You may find more information on birds in a box. Such as, does a box of birds weigh less if the birds are flying around? But I like helicopter in a box better.

 

[Guyzerr]

You may find more information on birds in a box. Such as, does a box of birds weigh less if the birds are flying around? But I like helicopter in a box better.

Mythbusters isn't quite scientific enough for my liking. I'll keep digging.

 

[BornReady]

I didn't know Mythbusters did an episode on this one. I guess it's more famous than I realized. I saw it on another forum. It got a lot more interest on that forum. There were a couple hundred posts in it.

 

[Guyzerr]

I didn't know Mythbusters did an episode on this one. I guess it's more famous than I realized. I saw it on another forum. It got a lot more interest on that forum. There were a couple hundred posts in it.

Yes they did. When I Googled for some info it came up. I'm still looking for a more reliable source.

 

[BornReady]

lol... I'm a reliable source.

 

[Guyzerr]

lol... I'm a reliable source.

Credentials please. :24:

 

[BornReady]

I flew one of those toy helicopters once.

 

[Guyzerr]

I flew one of those toy helicopters once.

I've been in a box a few times but that doesn't make me an expert. On second thought maybe it does. :24: