Coriolis Effect--Science or Superstition?

[TheBigDog]

Well, at least you acknowledge that I can and do think! :steering: But then you quote me so out of context that I wonder if you read what I wrote?

 

Let us assume that you and I are standing in yard together. We are each wearing a watch, and we st them to exactly the same time. We have a third watch that we tape to a ball. It is also set to the same time. We then walk to opposite ends of the yard and begin to throw the ball back and forth to each other. The ball is moving much faster than you and I. You and I are moving at the same speed. After throwing the ball back and forth for awhile, we stop and regroup. Comparing the three watches we see that they are all still reading exactly the same time. Satisfactory? Yes, for all normal purposes the three watches are still exactly in sync. But the watch that was being thrown back and forth actually kept time slower because of its increased velocity. This is an incontrovertible fact. But the amount of time difference is so incredibly small that we cannot see it. It is so small that in our every day lives it is completely irrelevant.

 

The same is typically true of the effects of the earth's rotation. It is there. That is (except for an elite few;) ) an incontrovertible fact. And this is not the only thing that falls into the category of "too small to notice". If I take a 500,000 ton weight to one side of the earth, and a 5 ounce weight to the other side of the earth, and drop them both from the same height at the same time, will they both his the ground at the same time? Observably, yes. Actually - no. Not only are both weights being attracted by the gravity of the earth, but the earth is being attracted by the gravity of both weights. The earth should actually fall toward the heavy weight faster than is does toward the light weight. Does this does not mean hat anyone would ever actually need to account for the difference because it is so imperceptibly small that it is totally inconsequential.

 

Close to the surface of the earth, with the random forces and general resistance of the atmosphere it is extremely difficult to demonstrate the effects of the rotation of the earth. Your experiment with the basketballs will prove nothing due the to variables in the experiment that you cannot control, and the incredibly small effect of the rotation of the earth on a body falling from even a few hundred feet. But just because you cannot detect it through normal observation does not mean that it is not there. That is why the pendulums work so well. They let a body essentially fall for a long period of time without ever landing. The high mass of the pendulum insures that it gets little interference from the atmosphere, and the long swing gives it a high inertia. Even with that you cannot see the rotation of the earth with just one or two swings of the pendulum. You need to watch it over a period of time. That experiment shows me the effects of the rotation of the earth. - that the earth is like a rotating disk.

 

Bill

[Erasmus00]

I was hoping to get you to work out how the bouncing ping pong ball will decelerate relative to the bulls eye.

 

It won't. You claim that the train is moving at a constant speed on level tracks. In this ideal situation, the ball will land directly on the bullseye, bounce and keep bouncing on the bullseye. An object in motion remains in motion at a constant velocity with no need for a force to accelerate it. Its Newton's first law.

 

But wait: this 'force (f)' is a misnomer. What is really happening on that 'disk' is the cutting off of force.

 

You are right about that. The coriolis "force" isn't a real force, but an apparent one. It comes about because we use Earth (a non inertial frame) as our reference.

 

If the caboose of a moving train is cut loose, it will begin to decelerate, relative to the locomotive.

 

Only because of friction. The more straight and level your tracks and the better the axle is greased, the slower the caboose moves away. In an ideal situation, it would stay right with the train.

 

There's a principle there, which applies to all terrestrial transport: Delta force causes delta travel.

 

This isn't true. Newton's 2nd law, Force = d p/d t, where p is momentum and t is time. More often, Force = m*a = m d v/d t, where v is velocity and m is mass.

 

Rearranging we see that F dt = m dv. Brief forces cause small velocity changes, not small position changes. You are going back to the mechanics of Aristotle.

 

So when you drop that ping pong ball it is like cutting the caboose loose. It ceases, briefly, to receive power via the train, and will experience a slight lag, relative to the continuously powered train.

 

First, on ideal tracks with an ideal train you wouldn't have to continuously power your train. Obviously, this isn't the case. Even keeping that in mind, if we can keep the train from accelerating during our experiment, the ball will fall on the bullseye. The air inside the train is moving with the train, as is everything else inside. There is no friction/resistance to push the ball back relative to the train, as there is in your caboose example.

 

If you're ever on an airplane, wait untill its levelled out and try throwing a coin up. If on a relatively slow train, the coin would move back slowly, on a much faster airplane, the coin should quite quickly move back. You'll find instead it goes more or less straight up and back down.

 

One that appeals to me is to take 100 or so basketballs up on a big boom near the ceiling of a basketball arena and drop them directly over a mark on the floor. If more basketballs come to rest West of the mark than anywhere else, you'd have support for Coriolis-ism.

 

This experiment is pretty flawed. The balls can take all sorts of random bounches, and will interact with each other. Odds are, most of the time they'll all roll away.

 

Try the following: build a cart and two tracks, one long and straight and one a nice smooth circle. The cart should be set up so you can launch it at the same speed everytime, (perhaps by having it compress a spring to a fixed length and then have the spring launch it). It should also have a built in launcher for a small metal ball that works on a short timer.

 

Now, first run the cart on the straight track, nice and level. Have the ball launch sometime during the run. You'll find that if your tracks are reasonably level, the ball will land right back in the cart.

 

Now, use the circular track. This time you'll find the ball won't land back in the cart.

 

By playing with your tracks and different angles, maybe building some ramps to test gravitational effects, you can learn a great deal of physics.

 

But it isn't having your toes in the dirt that makes you part of Earth--it is being within Earth's gravitational field. There is absolutely no difference to that gravitational field whether you are a bird or a turtle.

 

That simply isn't true. When you are making contact with the Earth, there is a great deal of friction between you and the surface. This drives you around in your circular motion. As soon as you aren't touching the Earth, that friction isn't there.

-Will

[Qfwfq]

Erasmus, you're so often in the habit of saying "That simply isn't true." and the likes, but when someone is arguing against accepted facts there's not much point in saying that kind of thing.

 

My contention is that this disk illustration is non-analogous to Earth.

If you understand the disk illustration, on what grounds do you claim the lack of analogy? I think that in your case you can only turn to experiment, as long as you do it in such a way that it could falsify the opinions about falling bodies deviating eastward, cyclones and anticyclones or oceanic currents, Foucault's pendulum.... :steering:

[cnewtongifford]

on what grounds do you claim the lack of analogy? QUOTE]

 

Qf: 1) The rules of motion on the disk are essentially different from the rules of motion 'on' Earth's surface (only on the disk is thereany material difference between angular vs linear velocity, expressed in physical momentum variances)

2) The math of the Coriolis formula is flawed (it fails to include the inarguable principle that 'a terrestrial cut-loose caboose tends to lose'--i.e: that the first component of Resistance to terrestrial motion is the mass of the object to be moved, which is distinct from everything commonly classed as friction).

 

The bouncing ball on a moving terrestrial train was the simplest illustration I could come up with to try and shed some light on this basic truth. It has now been over a week since anyone has spoken up. There have been 2 purported "rebuttals', no sign that even one person out there, anywhere in the world, understands that bouncing ball on the train.

 

So I have failed. I give up. This thread seems to have been killed. There is a difference in assembling around a campfire and discussing something--and assembling around a campfire and peeing on the fire.

 

Good night and good luck. CNG

[Qfwfq]

The rules of motion on the disk are essentially different from the rules of motion 'on' Earth's surface (only on the disk is thereany material difference between angular vs linear velocity, expressed in physical momentum variances)

The difference is in the sine of latitude. If you move toward the equator you are increasing your distance from the axis of rotation but this increase, for an element of distance ds along the meridian, is equal to ds times the sine of latitude.

 

The math of the Coriolis formula is flawed (it fails to include the inarguable principle that 'a terrestrial cut-loose caboose tends to lose'--i.e: that the first component of Resistance to terrestrial motion is the mass of the object to be moved, which is distinct from everything commonly classed as friction).

Well, if you like to believe that, good night and good luck. I just love the relief of the bladder after peeing on campfires. If you want to meditate upon the bouncing ball on a train, you might find it interesting to read Galileo's dialogue, he goes well into such matters.