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Science Question
nomss
Member UncommonPosts: 1,468
suppose a helicopter has infinite fuel and it is in the air, not moving. suppose a person is hanging down on a rope from this helicopter and he is facing north. Would he be facing south eventually if he stays like that?
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Comments
If it's a twisted rope yes as his weight would cause the rope to stretch. If not then all things being equal, no.
Bren
while(horse==dead)
{
beat();
}
North would be fixed if the rope doesn't twist.
The answer is basically no. If you keep your position and orientation you will not change yourself.Another great example of Moore's Law. Give people access to that much space (developers and users alike) and they'll find uses for it that you can never imagine. "640K ought to be enough for anybody" - Bill Gates 1981
If you put a jet plane on a tread mill, will it take off, or will the wheels just spin and it will stay in place?
The wheels would just spin. There isn't any lift under the wings (besides what could occur naturally from wind).
If you manage to throw an orange into space, would it decompose after a few months like on Earth?
Nope. The plane takes off. The force of the jet engines is all that matters. the tread mill would change the speed of the wheels spinning, but have no other effect.
You might want to add the condition of the thrusting of the jet engines into the question then.
I guess the thrust of the engines could have been implied, but the omittance of the thrust could have been a trap.
actually, gonna rephrase what I said
This is wrong, you need lift from etiher roll or the wings, without wind passing over the aileron or over the wings there is no lift and the plane would just crash at the end of the runway.
The only way this would work is if you would go faster than the threadmill, which would make this question useless, and you would still be wrong because the force of the jet engines would then NOT be all that matters, the wind over the wings = vertical lift.
It's a physics question. The correct answer is the plane takes off. I don't understand it, just know the correct answer is the plane takes off. You can google it.
This is simply a trick question and the answer can't possibly be right.
For there to be lift, you need wind over your wings. If you're on a treadmil you generate no lift, does your hair blow if you run on a treadmil? No. It does when you're freely running. No wind = no lift. It is impossible.
I'm sure someone has a video of a RC plane taking off from a treadmil, but this is only possible because it's going faster than the treadmil, thereby generating lift.
http://www.youtube.com/watch?v=XIsIzjVi7j4
And that is the end of the jet airplane debate. The wheels on an airplane only produce drag from the friction of their own bearings (with a combination of gravity and the level of the ground); the engine is what propels the plane. And none of that matters because jet engines can take-off vertically -- without an extended amount of runway space or space from a treadmill (very much like a rocket).
The person is just hanging down, rope is not being twisted. But the world is rotating though right? So won't the person eventually be facing somewhere else?
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The airplane does not generate forward momentum through the wheels, it generates it through the thrust of the engine/propeller. Basically the engine is pushing on the air around the airplane and will more forward regardless of the conveyor beneath it. In that case the air around the ariplane that the thrust of the rotor/prop/jet turbine is hitting is stationary relative to the airplane and that's where the forward momentum is generated.
Newton's third law states for ever action there's an equal and oposite reaction. Thus when the prop/jet turbine generates thrust it pushes on the air behind/around it and the air theoretically "pushes back" thus propelling the plane forward. If the engine put power to the wheels that were touching the conveyor then yes, the plane would remain grounded.
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The person should rotate with the earth.
Fere libenter homines id quod volunt credunt.
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The person is just hanging down, rope is not being twisted. But the world is rotating though right? So won't the person eventually be facing somewhere else?
Sorry but you have to go by th phrasing of your origonal question. Doesant matter if the world moves as you have to not move i.e. Keep your position the same therefore you rotate with the earth always. So your position never changes and you always face the same way as the poles afteralll do to.Another great example of Moore's Law. Give people access to that much space (developers and users alike) and they'll find uses for it that you can never imagine. "640K ought to be enough for anybody" - Bill Gates 1981
I see. So the helicopter being in the air is not enough for the person to be facing different direction? One would have to be outside of earth's hemishphere in order to witness this phenomena?
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Everything We Know about GW2:
http://www.mmorpg.com/discussion2.cfm/thread/287180/page/1
This is the correct answer.
People visualize it like a car on a conveyor belt, and think the jet engine is the same as a car engine, just something to move the wheels on the ground.
But the wheels have nothing to do with it when you're talking about a jet engine.
No, no matter how much the Earth rotates under you north is still north. The only way you would be facing south eventually is if you hung there long enough for a Geomagnetic Reversal. That is when the magnetic poles reverse and north and south switch places. It hasn't happened in recorded history but scientists do know it does happen about every million years or so over a span of 1,000 to 10,000 years. They figure the last one happened about 780,000 years ago.
Bren
while(horse==dead)
{
beat();
}
I think their confusion sets in because they assume the plane will now have to put forth double the effort to take off. People figure since the conveyor is going backwards the plane will now have to take off at 90 miles/hour instead of 45 miles/hour (numbers are examples only). But as I mentioned above, the plane is not putting power down through the wheels so it does not matter how fast the conveyor is going, the airplane will still thake the normal amount of power from the prop to get going.
A simple experiment you can do if you have a tread mill is start jogging at a steady pace and then put your hands on the hand rails and see how much effort you'll need to pull yourself forward with your hands. You'lll notice that it takes very little pull to get you to lurch forward as opposed to trying to outrun the conveyor of the tread mill.
No required quests! And if I decide I want to be an assassin-cartographer-dancer-pastry chef who lives only to stalk and kill interior decorators, then that's who I want to be, even if it takes me four years to max all the skills and everyone else thinks I'm freaking nuts. -Madimorga-
To answer the original question, there are two answers based on different assumptions:
1. The helicopter has unlimited fuel, but in all intensive purposes is a REAL helicopter. The rope is not wound. The individual does not attempt to move or change direction. Essentially, this makes the individual an extension of the helicopter. The helicopter is suspended in space by it's own power, however it maintains it's bearings based on gyroscopic instruments or gps fixes which operate within the realm of real physics. The pilot will hold his position using the instruments in the helicopter which are designed to keep it's position over the earth as it rotates. The bottom line is that as long as the helicopter maintains it's North heading and does not change position, the person suspended below it would remain facing north.
2. Either the helicopter is not using REAL instruments, or the individual is allowed to move independent of the helicopter. If either of these are the case, you are talking about having the ability to suspend an object in space independent of the earth and it's forces. Basically, to make this case you have to ignore gravity and several other physical laws. Then you can have a helicopter hold a man on a rope and their orientation will change with respect to Earth's magnetic north pole due to precession. In fact, the altitude of the helicopter and it's orientation would change as the earth rotated.
As a comment, the torque based precession of the helicopter is not a factor since it is cancelled by the helicopter's anti-torque rotor (tail rotor).
Edit: I forgot to mention that these are all in reference to Magnetic North unless it was perfomed on the declination line.
To the airplane on a treadmill:
There are two factors in this "problem": Airspeed and ground speed. With an airplane, they are independent of each other and actually have no real effect on the other. Ground speed is the rate at which an airplane travels over the physical earth, while airspeed is the rate at which air flows over an aircraft. Only airflow over airfoil can produce lift and therefore only airspeed can cause an airplane to fly. A treadmill produces an artificial "ground speed" which means that unless you also have a wind tunnel, an airplane does not take off if held stationary over a rotating treadmill.
The person is just hanging down, rope is not being twisted. But the world is rotating though right? So won't the person eventually be facing somewhere else?
Sorry but you have to go by th phrasing of your origonal question. Doesant matter if the world moves as you have to not move i.e. Keep your position the same therefore you rotate with the earth always. So your position never changes and you always face the same way as the poles afteralll do to.I see. So the helicopter being in the air is not enough for the person to be facing different direction? One would have to be outside of earth's hemishphere in order to witness this phenomena?
Its a bit late here now but essentially yes as you are still being effected by the Earths gravity field which causes you to rotate with it. So to get the effect you want your helecopter and rope guy needs to leave the Earths atmosphere into high Earth Orbit.Another great example of Moore's Law. Give people access to that much space (developers and users alike) and they'll find uses for it that you can never imagine. "640K ought to be enough for anybody" - Bill Gates 1981
I think my post accounted for most of the airplane debate, it just wasn't very developed.
To explain the idea of a jet on a treadmill more simply, remember that the engine(s) are what compensate for the speed of the treadmill underneath the wheels. The faster the treadmill, the more thrust the engines need to generate to compensate for the speed of the treadmill, or else the plane will be ejected from the rear of the treadmill (like someone accidently setting the initial speed way too high). Once the engines build up enough thrust whilst compensating for the speed of the treadmill, the aircraft will take off.