Re: At what point is research just plane stupid?
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Originally Posted by
scaryjim
When did I say anything that could be construed that way? I'll happily take refutals of my science, but please don't make up ridiculous nonsense then try to put it in my mouth... :rolleyes:
No made up at all. Just following your logic with Newton's third law et al.
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
Top_gun
... Just following your logic with Newton's third law et al.
No, you're really not. Newton's third law means we don't have gravity? What?
I honestly have no idea what you're trying to say any more... *sigh*
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
scaryjim
No, you're really not. Newton's third law means we don't have gravity? What?
I honestly have no idea what you're trying to say any more... *sigh*
I was thinking of the fictional centrifugal force allowing me to walk on air.
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
Top_gun
I was thinking of the fictional centrifugal force allowing me to walk on air.
a) it's not fictional, it's a requirement of Newton's third law
and
b) when have I said it allows you to walk on air?
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
Top_gun
I was thinking of the fictional centrifugal force allowing me to walk on air.
OK, so....Ttasky Pseudo-Science here...
If you weigh yourself at the North Pole, then go down and weigh yourself at the Equator, you will be lighter at the latter.
The understanding is that centrifugal force from the Earth's rotation causes this.
Still a fictional force? :)
Re: At what point is research just plane stupid?
Isn't that just because your closer to the gravitational force at the poles? Just a matter of distance....
Re: At what point is research just plane stupid?
Right, everyone, please stop. I have certain people's posts on ignore by default, but even without seeing those this is becoming a joke. If people bothered to read the wiki entries for centripetal and centrifugal force I reckon we could quickly put this pointless pedantism to bed.
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Originally Posted by wikipedia
A centripetal force (from Latin centrum, "center" and petere, "to seek"[1]) is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous center of curvature of the path. Isaac Newton described it as "a force by which bodies are drawn or impelled, or in any way tend, towards a point as to a centre".[2] In Newtonian mechanics, gravity provides the centripetal force responsible for astronomical orbits.
One common example involving centripetal force is the case in which a body moves with uniform speed along a circular path. The centripetal force is directed at right angles to the motion and also along the radius towards the centre of the circular path.[3][4] The mathematical description was derived in 1659 by the Dutch physicist Christiaan Huygens.[5]
In the case of an object that is swinging around on the end of a rope in a horizontal plane, the centripetal force on the object is supplied by the tension of the rope. The rope example is an example involving a 'pull' force. The centripetal force can also be supplied as a 'push' force, such as in the case where the normal reaction of a wall supplies the centripetal force for a wall of death rider.
Newton's idea of a centripetal force corresponds to what is nowadays referred to as a central force. When a satellite is in orbit around a planet, gravity is considered to be a centripetal force even though in the case of eccentric orbits, the gravitational force is directed towards the focus, and not towards the instantaneous center of curvature.[9]
This BS about centrifugal forces not existing is only true in the case where you look at things in an inertial frame of reference that excludes any motion, including rotation. This is a problem for several other mechanical situations, and also relativity etc. It is always important to analyse things using the correct frames of reference for the problem at hand.
Quote:
Originally Posted by wikipedia
In Newtonian mechanics, the centrifugal force is an inertial force (also called a 'fictitious' or 'pseudo' force) directed away from the axis of rotation that appears to act on all objects when viewed in a rotating reference frame.
The concept of the centrifugal force can be applied in rotating devices, such as centrifuges, centrifugal pumps, centrifugal governors, and centrifugal clutches, and in centrifugal railways, planetary orbits, banked curves, etc. when they are analyzed in a rotating coordinate system. The term has sometimes also been used for the force that is a reaction to a centripetal force.
The centrifugal force is an outward force apparent in a rotating reference frame; it does not exist when measurements are made in an inertial frame of reference.[1]
All measurements of position and velocity must be made relative to some frame of reference. For example, if we are studying the motion of an object in an airliner traveling at great speed, we could calculate the motion of the object with respect to the interior of the airliner, or to the surface of the Earth.[2] An inertial frame of reference is one that is not accelerating (including rotation). The use of an inertial frame of reference, which will be the case for all elementary calculations, is often not explicitly stated but may generally be assumed unless stated otherwise.
In terms of an inertial frame of reference, the centrifugal force does not exist. All calculations can be performed using only Newton's laws of motion and the real forces. In its current usage the term 'centrifugal force' has no meaning in an inertial frame.
In an inertial frame, an object that has no forces acting on it travels in a straight line, according to Newton's first law. When measurements are made with respect to a rotating reference frame, however, the same object would have a curved path, because the frame of reference is rotating. If it is desired to apply Newton's laws in the rotating frame, it is necessary to introduce new, fictitious, forces to account for this curved motion.
In the rotating reference frame, all objects, regardless of their state of motion, appear to be under the influence of a radially (from the axis of rotation) outward force that is proportional to their mass, the distance from the axis of rotation of the frame, and to the square of the angular velocity of the frame.[3][4] This is the centrifugal force.
Motion relative to a rotating frame results in another fictitious force, the Coriolis force; and if the rate of rotation of the frame is changing, a third fictitious force, the Euler force is required. Together, these three fictitious forces are necessary for the formulation of correct equations of motion in a rotating reference frame[5][6] and allow Newton's Laws to be used in their normal form in such a frame.[5]
which is basically everything that has collectively been said by everyone in the previous posts. So please stop winding each other up and realise you are all saying the same thing, but failing to be consistent in understanding and acknowleding the differences in your respective frames of reference.
In the case of the airplane above. In terms of a person walking up and down the airplane, they move in a straightline. Inside the inertial frame of reference everything is linear. But to the observer on the ground, outside of that frame of reference, the plane, and the person inside it, are following an arc trajectory to maintain constant height above the earth. That trajectory cannot be explained without the additional pseudo forces - in this case gravitational pull acting as the required force.
As the article states centrifugal force is a correct usage of the equal and opposite force to centripetal. And it gets better because that reactive centrifugal force IS always present, and does not depend on frames of reference:
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Originally Posted by wikipedia
In classical mechanics, a reactive centrifugal force forms part of an action–reaction pair with a centripetal force.
In accordance with Newton's first law of motion, an object moves in a straight line in the absence of any external forces acting on the object. A curved path may however ensue when a physical acts on it; this force is often called a centripetal force, as it is directed toward the center of curvature of the path. Then in accordance with Newton's third law of motion, there will also be an equal and opposite force exerted by the object on some other object,[1][2] such as a constraint that forces the path to be curved, and this reaction force, the subject of this article, is sometimes called a reactive centrifugal force, as it is directed in the opposite direction of the centripetal force.
Unlike the inertial force or fictitious force known as centrifugal force, which always exists in addition to the reactive force in the rotating frame of reference, the reactive [centrifugal] force is a real Newtonian force that is observed in any reference frame. The two forces will only have the same magnitude in the special cases where circular motion arises and where the axis of rotation is the origin of the rotating frame of reference. It is the reactive force that is the subject of this article.[3][4][5][6]
It is all there in the articles. So a centrifugal force can be rightly be regarded as pseudo/ficticious, and also rightly as real and observable. Let's leave it there shall we?
And to link it back to the OP and thread title. A little research before posting might have been beneficial here - in this case lack of research is where we risk the plain stupid coming into it.
https://en.wikipedia.org/wiki/Centripetal_force
https://en.wikipedia.org/wiki/Centrifugal_force
https://en.wikipedia.org/wiki/Reacti...he_turning_car
Re: At what point is research just plane stupid?
From now on let's only acknowledge the strong / weak nuclear, electromagnetic and gravitational forces.
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And to link it back to the OP and thread title. A little research before posting might have been beneficial here - in this case lack of research is where we risk the plain stupid coming into it.
Yeah the issue here is this idea is flawed, based on flawed assumption that cross wind landings are hard due to the cross wind, rather than the gusting nature of the wind in question. That it would be easier to land in a curve than handle a cross wind in the circumstances an airliner must be able to land say with an engine out.
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
Ttaskmaster
OK, so....Ttasky Pseudo-Science here...
If you weigh yourself at the North Pole, then go down and weigh yourself at the Equator, you will be lighter at the latter.
The understanding is that centrifugal force from the Earth's rotation causes this.
Still a fictional force? :)
My understanding is the Earth is not a proper sphere so yes there will be differentials in weight.
I still have my old A'Level Physics text books by Tom Duncan and there is no mention of centrifugal force whatsoever in the index. Plus the fact that my old Physics teachers instilled in me there was no such thing as centrifugal force. However, I'm more than happy to accept Ik9000's explanation on this issue in terms of isolated mechanical forces in a particular timeframe. I suppose I could contact an ex-school colleague, who is now Head of Physics in a University, for a second opinion...
Re: At what point is research just plane stupid?
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Originally Posted by
ik9000
Right, everyone, please stop. I have certain people's posts on ignore by default, but even without seeing those this is becoming a joke.
Yeah, but I'm thick, so all I can do is joke and hope that it helps people enjoy the thread a bit rather than it descending into a blazing argument.
I also assume I'm one fo thsoe on ignore anyway, but hey...
Quote:
Originally Posted by
TheAnimus
From now on let's only acknowledge the strong / weak nuclear, electromagnetic and gravitational forces.
I think the Special Forces might take issue with your lack of acknowledgment...!! :lol:
Quote:
Originally Posted by
shaithis
Isn't that just because your closer to the gravitational force at the poles? Just a matter of distance....
From sciencey people at NASA:
"The effective acceleration of gravity at the poles is 980.665 cm/sec/sec while at the equator it is 3.39 cm/sec/sec less due to the centrifugal force. If you weighed 100 pounds at the north pole on a spring scale, at the equator you would weigh 99.65 pounds, or 5.5 ounces less".
So centrifugal force is real and it's the cause in this instance... apparently.
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
Ttaskmaster
From sciencey people at NASA:
"The effective acceleration of gravity at the poles is 980.665 cm/sec/sec while at the equator it is 3.39 cm/sec/sec less due to the centrifugal force. If you weighed 100 pounds at the north pole on a spring scale, at the equator you would weigh 99.65 pounds, or 5.5 ounces less".
So centrifugal force is real and it's the cause in this instance... apparently.
Imagine the Earth disappeared, what would happen to you? You've fly off into space at a constant speed in a straight line (Ignoring the effects of other bodies). It requires force, caused by gravity, to keep you moving in a circle. This force causes an acceleration, meaning a change in speed or direction.
The 'effective acceleration' is the key. Assume the Earth were a sphere, and consider two masses at different points on the surface. One at the equator, and one at a higher latitude. Both bodies travel in a circle, relative to the Earth. The one at the equator travels faster, since it's circle is larger. As a result, it requires a larger force to change it's direction. Gravity, however, on our model sphere, is constant. Effective acceleration, being caused by the remainder of the force pulling you toward the planet, is reduced.
You can visualize the same thing by considering orbital dynamics. Accelerate a body to a high enough speed, and eventually the force from gravity equals the amount needed to keep the orbiting body moving in a circle. The effect is what's called 'weightlessness'. Reduce the speed, and the body will fall back toward earth.
Re: At what point is research just plane stupid?
The BBC has published a follow-up article; still not convinced!
http://www.bbc.co.uk/news/magazine-39643292
Re: At what point is research just plane stupid?
So, the one thing we can take out of this is: if you want to lose weight, move to the equator.
I'll tell the wife.
Re: At what point is research just plane stupid?
Quote:
Originally Posted by
Smudger
So, the one thing we can take out of this is: if you want to lose weight, move to the equator.
I'll tell the wife.
Smudger: Honey, that dress just isn't working on you. We're moving to Ecuador.
Re: At what point is research just plane stupid?
Quote:
Henk replies: A higher speed will be necessary, indeed.
Take-off and landing run will increase because of this and the time that an aircraft spends on the runway will be about five to ten seconds longer.
So still absolutely zero mention of the fact most wind gusts are the problem rather than pure cross wind. No mention about the extra wear on the airplane. Even the remark about the ILS sounds shoddy as hell. (No you don't want your ILS moving...)
Re: At what point is research just plane stupid?
From the follow up:
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It is like a concept car in a car exhibition - it will not be implemented exactly like this, but we learn a lot from the ideas, from simulations and, later on, practical tests.
This should have been highlighted more. They might find out something useful [accidentally] even if circular runways have too many problems.