Why does a helicopter float motionless but still consume gas?

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SUMMARY

A helicopter can hover motionless while still consuming fuel due to the work done by its rotor blades, which push air downwards, creating lift to counteract gravity. This results in a net acceleration of zero, but energy is expended in moving air and generating heat. The discussion highlights the importance of understanding reference frames in analyzing work done, emphasizing that even when stationary relative to the ground, the helicopter is actively working against gravitational forces. The aerodynamics involved are complex, but the fundamental principles of Newton's laws and the definition of work are crucial for comprehension.

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When a helicopter float motionless the work done on it is zero.But why does it still consume energy?A similar question is why when we hold still a weight, we must consume energy(we feel fatigue)?
 
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It is not true that no work is being done. The rotor blades do a LOT of work pushing air down and thus causing the helicopter to accelerate upwards at 9.80665 m/sec/sec in a gravitational field that is causing it to accelerate downwards at the same rate. So ... helicopter stays motionless, air moves. From the frame of reference of the air, the helicopter is moving quite a bit and is doing a lot of work.

I think the aerodynamics of it all may be a bit more complicated than that simple explanation, but you get the idea ...

The exact same question was asked recently in the form of "if I push a box across the floor against friction, I am doing work, but in MY frame of reference the box isn't moving so I'm actually NOT doing any work. What gives?" In his frame of reference he is doing work moving the floor under him. In both his question and yours, you can't get rid of the work being done just by changing frames of reference.
 
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fxdung said:
When a helicopter float motionless the work done on it is zero.But why does it still consume energy?A similar question is why when we hold still a weight, we must consume energy(we feel fatigue)?
Both are inefficient ways to generate a static force. The energy goes into moving air and heat.
 
fxdung said:
When a helicopter float motionless the work done on it is zero.But why does it still consume energy?
They don't always consume energy when floating motionless... 😉

http://avia-proekt.ru/img/ch7_9.jpg
1564755804228.png
 
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phinds said:
I think the aerodynamics of it all may be a bit more complicated than that simple explanation, but you get the idea ...
Due to the nature of the question, the aerodynamics are unimportant and the Newton's 3rd law + definition of work (power) explanation is all that is needed.

If I had a quibble it would be on the need to discuss reference frames here. To me it's about the proper definition of the system being analyzed. A helicopter is not a book sitting on a table, it's a fan sitting on a table. The fan does work because it's a fan!
 
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Why does a helicopter float motionless but still consume gas?

If you turned the engine off, would it continue to float?
If not, why not? (Please write a sentence for that and not a one-word answer)
 
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fxdung said:
When a helicopter float motionless the work done on it is zero.
Helicopters dont float, They hover

Answer @Vanadium 50 's Q's above
 
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A.T. said:
The energy goes into moving air and heat.
Yup, that description couldn't be much closer. . . as to how the real deal works .

.
 

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