Talk:Gravitron

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[edit] Gravitron vs Starship 2000 vs Starship Exodus

What are the differences between the three? The only one I know of is that The floor on the Gravitron drops down whereas onteh starship exodus it does not. I also know that the Gravitron was much bigger (handling 1000 passengers per hour).

The Gravitron comes to our city fair, and I really don't think the floor drops.FrogTape 23:41, 9 April 2007 (UTC)


"These walls are fitted with cushions for each individual rider, on top of sliders which move up and down at Pseudo-random intervals."

I believe this is untrue. I've ridden the gravitron. the walls are angled outward at the top, so these panels are pulled upward by the centripital force. as the gravitron speeds and slows the force changes and the panels shift.

I think the panels are partly controlled by mechanical devices, since they move in different ways at the same time, but I do agree that the "pseudo-random" part should be changed. That phrase links to a page about cryptological applications of pseudo random number generators, anyway, so it has nothing to do with the Gravitron context. 12:50, 8 September 2005 (UTC)

I think the ridiculous discussion at the bottom of the Gravitron page should be removed. Centrifugal force exists. The guy who wrote that after his 1st physics class has probably made it to the 2nd one (the one frames of reference!) and forgot to correct this. Even if he was right, the corresponding polemic discussion doesn't belong on that page.

The discussion has been removed. I also see that the wording was changed at some point from "centrifugal force" to "centripetal force". I'm not a physics expert myself and don't feel like becoming one, so I don't know which one is more correct. Seems to me it should be centrifugal, since the mats move away from the center of the gravitron, but I'm not certain. I don't really have a great grasp of what centripetal force is, other than it's what keeps satellites in orbit (I think). Anyone know the right answer? Kafziel 15:57, 25 January 2006 (UTC)
It is Centripetal force. When objects are moving in a circular path, they are always accelerating (that is, changing direction). Without some force to change that objects direction, intertia would keep it moving in a straight line. The centripetal force (force directed inward to the center) is the walls of the Gravitron, which "push" toward the center of the circular path. The mats sliding outward is just a result of them not being pushed in as much. Centrifugal force is the opposite--it is force away from the center. There aren't any actual instances of centrifugal force that I know of. ~MDD4696 17:36, 25 January 2006 (UTC)
Ah, I see. This is one of the concepts I always hated in architecture classes; it seems so childish to me to think that inanimate objects exert opposing forces (rather than retaining a higher level of inertia than the object acting upon them). As though every floor in a house is sentient and tiny magical people inside the wood are waiting for us to walk on them so they can push back against our feet. (Or, in this case, tiny magical people in the walls of the Gravitron, actively keeping the sleds from flying out, rather than just saying that the molecules in the walls are held together tighter than the force trying to break through them.) The whole thing seems completely absurd to me, like the kind of explanation they would have come up with in the dark ages. But I guess that's why I'm not a physicist. :)
Thanks for the explanation. Kafziel 18:18, 25 January 2006 (UTC)

[edit] It is NOT centrifugal force

Centrifugal force is what causes a rotation. For example, if you have a ball on a string and swing the ball in a circle, the string exerts centrifugal force on the ball. Centripetal force is what the riders on a gravitron feel. Centripetal force is a pseudo-force brought about by presense in a rotating reference frame. It is a result of an object's tendency to move in a straight line. In reality, what you are feeling on the gravitron is an effect of inertia, but if you measure things relative to the rotating reference frame, ie the body of the gravitron, there is a net effective force outward due to the rotation. It's a very real and measurable quantity, and has NOTHING to do with centrifugal force.

I don't follow you. If it's a "pseudo-force", as you say, how can it be effecting anything? If someone is effected by it, then it's a force, and there's nothing pseudo about it. Which is it? Kafziel 17:43, 27 January 2006 (UTC)
It all depends on your frame of reference. From outside the ride, we see that the rider's inertia wants to keep moving in a straight line, but the walls keep pushing him off of that path (the walls are like the string in the example). To make the rider move in a circular path, this force must be directed toward the center of the circle—the very definition of centripetal force. Now, if you change your frame of reference to be inside the Gravitron, things get all messed up, because the Gravitron is no longer rotating, but the "outward force" is still there. You might call that centrifugal force, but since we first started with a frame of reference outside the Gravitron, we know it's a result of centripetal force. ~MDD4696 18:01, 27 January 2006 (UTC)
Ummmmm...okay. Sure. Kafziel 18:11, 27 January 2006 (UTC)
To clarify here, centrifugal force is an effect of inertia, not a reaction force to the centripetal force.


The person riding a gravitron is within the rotating reference frame. Therefore, the relevant quantity is that felt by the person, which is a centrifugal pseudo-force. Newtonian physics is only REALLY correct in an inertial reference frame, so as a correction, when you try to describe what is felt within a rotating frame, you introduce pseudo-forces, which don't fit all the criteria for a real force, but are a way to explain the effects of the non-inertial reference frame. To say you feel an effective 4 g's due to centripetal force is simply wrong - the force a person "feels" within the gravitron is outward, and thus cannot possibly, by definition, be a centripetal force. This force would be felt whether the person is touching the walls or near the center being accelerated towards the walls. Also, for interest's sake, there are two other possible pseudo-forces within a rotating frame - the azimuthal and coriolis forces.

This is correct :). However, the way the article is currently worded is also correct... so... we're good then? ~MDD4696 00:34, 28 January 2006 (UTC)
Well, if you guys both agree then it's fine with me. All I care about it is that you get in, it spins around, and kids puke. If carnies can run it, it damn sure isn't rocket science. :-) Kafziel 02:04, 28 January 2006 (UTC)
Technically the wording is correct, however it is misleading. It makes it seem as if centrifugal force is what makes you feel the 4 G's. It isn't. You would feel the 4 G's whether you were touching the wall or not, so the force cannot be a result of centrifugal force and is due solely to the rotating frame of reference.

I still think the wording should be changed from centripetal to centrifugal, because the way it's worded right now is very misleading. And yes, IAAP.

[edit] It is Centripetal

Centripetal= mass times velocity squared over the radius of a circle. The reason you feel the G's is because of the force exerted from the wall onto you (normal force). If the wall wasn't there, then you wouldn't stay in the circle and therefore would'nt feel the G's..

You would feel the force if there was no wall - within that frame of reference you would be accelerating outward. Centrifugal force is BALANCED by centripetal force, so that the net force (again in the frame of reference) is zero. Centripetal force is always toward the axis of rotation, and centrifugal force is always away from it. I'm sorry but this is such a commonly misunderstood concept that anyone who isn't a physicist has no business discussing it. The wording should be centrifugal.

I agree. Centripetal froce is what pushes an object of of a spinning object.FrogTape 23:40, 9 April 2007 (UTC)

[edit] Walking

All you people are losers, you sound like the comments from youtube. You’re arguing over what to call it. It just depends on the reference frame. In a rotating reference frame it is the real centrifugal force and in the inertial frame it is the imaginary centrifugal force that is just your perception of 4gees of acceleration towards the center of the ride. And on to more important matters: when I was on one of these things the (dj) ride controller gave a demonstration by walking on the floor out of his booth(near the center the small diameter makes the forces negligible.) and walked out a few feet until he just took one more step and was standing on the railing at almost 90deg to the horizontal. Is it just me or is that really cool. And he didn't even seem seasick. It looked like one of the scenes from a cheap old vamp movie. 71.112.30.41 06:22, 21 March 2007 (UTC)

There is a starship 2000 at the western Idaho fair [Boise fairgrounds].