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Helicopter and a turntable

mrSHEiK124

mrSHEiK124

Lifer
You've got a helicopter on a turntable that's spinning at the same speed and opposite direction as the heli's rotors. Does the helicopter take off?

see the first reply -DrPizza
 
Of course. This one is easy because the rotors are providing the lift in the scenario. If it were a plane and there was no wind running over the wings, the plane wouldn't take off.
 
A rabbi, a priest, and a minister walk onto a treadmill. Who takes off and gets to Heaven first?


A shrimp runs on a treadmill. Does it take off?
 
Originally posted by: Jeff7
A rabbi, a priest, and a minister walk onto a treadmill. Who takes off and gets to Heaven first?


A shrimp runs on a treadmill. Does it take off?
Click to expand...

Jews don't go to heaven.
 
The answer would seem quite clearly to be that no it does not take off, the blades are not moving relative to the air therefore no thrust is generated therefore no takeoff. Seems pretty simple, the only real "trick" is that people are gonna be stupid and blurt out the same answer as the plane on a treadmill instead of actually thinking it through.
 
Originally posted by: Quasmo
Of course. This one is easy because the rotors are providing the lift in the scenario. If it were a plane and there was no wind running over the wings, the plane wouldn't take off.
Click to expand...

So you're saying that this problem is just as easy and uncomplicated as the plane that *does* take off from a treadmill? 😀
 
Originally posted by: FlashG
Originally posted by: Jeff7
A rabbi, a priest, and a minister walk onto a treadmill. Who takes off and gets to Heaven first?
Click to expand...
The terrorist does dummy.
Click to expand...
What if he's in the helicopter?😛


Originally posted by: BrownTown
The answer would seem quite clearly to be that no it does not take off, the blades are not moving relative to the air therefore no thrust is generated therefore no takeoff. Seems pretty simple, the only real "trick" is that people are gonna be stupid and blurt out the same answer as the plane on a treadmill instead of actually thinking it through.
Click to expand...
Indeed, because this problem is defined more clearly. The plane vs treadmill answer changes, depending upon the assumptions in the original problem, such as, is there friction, do the wheels have mass, do the wheels have rotational inertia, and exactly what the treadmill speed is a function of.

Here, it's clearly defined, and the problem itself is simpler. In this case, the helicopter blades will be kept stationary relative to the air. Helicopter doesn't take off.



Bagels.


 
Originally posted by: cKGunslinger
Originally posted by: Quasmo
Of course. This one is easy because the rotors are providing the lift in the scenario. If it were a plane and there was no wind running over the wings, the plane wouldn't take off.
Click to expand...

So you're saying that this problem is just as easy and uncomplicated as the plane that *does* take off from a treadmill? 😀
Click to expand...

Actually, yes, I think he is.
 
Relevant diagram:

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................... __\||/____......
.\\...............|'-|--| .\\....\.....
..\ \_...........|--|---|..\\ ....\....
../ L \____,/-------\___\___
.|LOL|-------------O----- ----,\..
..\ L /______,---''-----------, /...
../ /.............\_________ ,/....
.//.............____//___ __\\__/.
 
Originally posted by: Quasmo
Of course. This one is easy because the rotors are providing the lift in the scenario. If it were a plane and there was no wind running over the wings, the plane wouldn't take off.
Click to expand...

Actually this is incorrect. There would be no wind running over the helicopter's blades since the blades would be stationary in this example. The helicopter is attached to a turntable that spins in the opposite direction as the rotor. The rotor would have no velocity in reference to the surrounding air.
 
Helicopters don't have to rely on air speed, only their rotors speed. Tail rotor would just have to work harder to balance the heli during take-off, but otherwise it would work.
 
Originally posted by: potato28
Helicopters don't have to rely on air speed, only their rotors speed. Tail rotor would just have to work harder to balance the heli during take-off, but otherwise it would work.
Click to expand...

It doesn't sound as if the rotors would be turning at all, with relation to the Earth, at least.

It doesn't seem logical that just the difference in rotational speed between the helicopter body and the rotor would cause lift.
 
Originally posted by: potato28
Helicopters don't have to rely on air speed, only their rotors speed. Tail rotor would just have to work harder to balance the heli during take-off, but otherwise it would work.
Click to expand...

You don't understand the question. The helicopter's tail rotor would be useless since the helicopter is anchored to a turntable that is turning at an equal and opposite speed of the main rotor. The main rotor would have no velocity in relation to the outside air.
 
In order to be equivalent to the plane on the treadmill, the helicopter would have to be on roller balls or circular arranged wheels
 
Think about it more carefully. All that is required for the helicopter to take off is that the rotors moves at a certain velocity, which we assume it reaches, relative to the air directly around the rotor.

The velocity of the turntable would not come into the equation at all.

Thus, the helicopter would take off.

 
Originally posted by: maxster
Think about it more carefully. All that is required for the helicopter to take off is that the rotors moves at a certain velocity, which we assume it reaches, relative to the air directly around the rotor.
Click to expand...

why do you assume that?
 
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