Physics of a Zero- G

Brett, I'm only 25 so I hear ya about record players being ancient. Wow, wierd to hear how old people are. No offense but I had you pegged for a lot older, you just sound wise beyond your years sometimes. Maybe its the engineering. But ANYWAY...

The diameter that the outside cars have to flip over is larger than that of the inner diameter, yet the row is one unit, so they move together, they are the same speed, just the outer cars have to travel a larger diameter in terms of rotation.

Apollo was right.

Thanks to all for clearing up, I agree w/ Apollo as well. And for records being ancient, I am all of 26 and still buy them. New ones by new bands. Hmmmm.

Use the carousel example and it's more apro-po'(sp?). Rides on the inside row horses, while on the same moving disk, are not traveling as fast as riders on the outside rows. It's that simple.

Oh...and a *some* vinyl sounds better than plastic disks!;)

Wood - anything else is an imitation

This discussion brought to you by your engineering term for the day.....

"Coriolis acceleration"

- Having nightmares/flashbacks yet, Brett?

Later,
EV

*twitch* I have ...AHH ... no idea what you're ... *twitch* ... talking about EV, I loved Engineering Physics *spontaneously punches self*.

That was evil man ...

AA - Yea, jerk is triple integral of location, which would make it a physical thing that the two will be different because of their different locations, but still, the body interprets it differently. You want a good example of the body experiencing jerk differently? I loved Steel Phantom and didn't find it dabilitatingly (sp?) painful ... while I did find X that way. Both are very contrary to popular opinion here, but me and everyone else here experienced the same first, second and third integrals of position (speed, accel and jerk for those that are trying to follow this WAY too technical discussion!). Even beyond that, I heard somewhere on this site is a non-CP fan that didn't experience massive head trauma on Viper SFGAdv! ;) So while you may take the same forces, your body weight, height, ability to self-balance (which I don't have in one ear) and other factors affect how you interpret it ... floaty, whippy, boring, painful, etc.

About record players, my parents have one and I hear that everyone says they sound better than CDs but I don't listen to anything on a regular basis that requires that much musical precision - Green Day, Reel Big Fish and other punk and ska bands are more about remembering how it sounded live than actually listening to what's coming out of the speakers in my opinion - and you can't beat your memory of live for quality!! But I just enjoy faking like I don't know what they are cause it usually makes other people feel old ;)

And many thanks to Shane! I look 14 so its not too often I get told I'm OLDER than I am! Thanks! *** Edited 1/22/2004 7:59:55 PM UTC by Impulse-ive***

Triple integral of location? First, second, and third integrals? Please explain those . . .

If you take position as a function of x, like of a particle. Say, a straight line movement in terms of meters and seconds:

6x

Now, at an x value of 2 seconds, the position of this "particle" is 6 * 2 = 12 meters

To find the speed at that moment of the particle, integrate ...

3x^2

Now, the speed is 3 * (2^2) = 12 m/sec

To find the acceleratioin of that particle, double-integrate:

x^3

So, acceleration is 2^3 = 8 m/sec/sec

To find the jerk which is more like what you feel when you reverse your momentum in a car - like accelerating fast, then hitting the brakes, or what your head experiences when X begins to throw your body to the left but ... UH OH! There's a headrest there that violently and instantly brings your head to a stop ...

(1/4)x^4

So jerk is (1/4) (2^4) = 4 m/sec/sec/sec

These are all major formulas used in figuring out comfort in roadways, trains, bridges, and yes, all roller coasters. Jerk is one of the more important ones, but very few people know about it specifically, but the first time they bang their head off a restraint, you learn about jerk REAL fast!!

Nope.

If position of particle follows the function 6x, its speed is a constant 6 meters a second. There is no acceleration and, therefore, no jerk.

I think Brett meant "jerk is the third derivative of position" or conversely "position is the third integral of jerk". He had the integrals/derivatives reversed.

Yes.

The particle starts at 0 and moves at 6x, you wanna tell me how it doesn't accelerate? If it's not moving to start, it can't gain speed without some kind of acceleration !

Um, I'm not sure if I have the names mixed up or not, I know the numbers, I really don't care enough about calc to know the names, so what I know is if you put three of those squiggles before a funciton that describes movement of a particle in space and evaluate it over a certain interval (usually that interval is time) you can find its jerk by that equation. (And two squiggles gives accel, and one gives speed)

Edit: Link to information about jerk: http://www.tompotter.us/jerk.html *** Edited 1/22/2004 9:12:37 PM UTC by Impulse-ive***

Very simply, moving at a constant speed (6x in this instance) implies no change of speed. A change in speed during an interval of time is acceleration, without change, there is no acceleration.

You're apparently aware of integrals -- placing the "squiggles before a function," as you stated, is integrating. However, speed, acceleration, and jerk are all derivatives of position.

I'm lost ... I'm tryin to work this out while I'm designing a bridge ... some bridge in Waynesburg, Pa is gonna end up with a Zero-G roll in the middle of it ....

Whatever, you're right, I'm wrong, I give up. *Retreats to the corner never to try and sound like I know what I'm talking about again*

Velocity (a.k.a. Speed) is the rate of change of distance.

Acceleration is the rate of change of velcoity.

Jerk is the rate of change of acceleration.

Practical Example

In a car, from a stop-light, lightly step on the gas. You are now experiencing steady acceleration. Now, floor it. The change of acceleration that you feel is jerk.

Later,
EV

Brett, NEVER GIVE UP! NEVER SURRENDER!!! I dunno... I love these threads where physics and mechanics actually come into play. You know what you're talking about, I know what you're talking about, I know what I'm talking about; my problem is making others understand what I'm talking about. Know what I'm talking about?

I also love the physics threads, and great example EV. It would be interesting to know how many CBers are former/current engineering students, and furthermore, how many started wanting to design coasters. It seems like a lot.

*peaks back out of corner of shame*

I just get really frustrated when I know a concept, I've worked with it before, I've helped with design work on it for a $4 billion dollar real-world project, and I still get the math wrong. I may be an engineering but I #%#&%ing HATE math!!!

EV's example is exactly correct. Now, coming back to my example, because the functions of the two seats are different, their jerks will be different, because the outer seat, BEACUSE of its rigid connection to the inner seat must increase its rate of acceleration through the spin to keep up.

Shane - I hear ya ... just read this thread! And look for any other technical ones that either Impulse-ive or PittDesigner (my old name) are in! I always come at least 90% of the way in concepts, but I can never express myself in words ... If I could come through the screen and use my hands and a pencil and paper, no problem, but flat out words are a rough fit for physics and engineering.

Yea, I basically got into engineering because I wanted to design coasters. I actually went into school specifically stating that I was never going to be an engineer no matter what... 4 1/2 years later, I just got my degree in the mail :) I really wanted to do marketing or just business, like running a medium-sized business, or an amusement park. That's one thing I really came to realize through my engineering semesters, is that there is such a small market for designing coasters anyway, you really gotta love the math and the engineering part of it. For me, park management is more the way to go - real life RCT is my dream job now. Hopefully someday ...

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Impulse-ive said:

EV's example is exactly correct. Now, coming back to my example, because the functions of the two seats are different, their jerks will be different, because the outer seat, BEACUSE of its rigid connection to the inner seat must increase its rate of acceleration through the spin to keep up.

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Not that anyone should believe me more or less because of it, but I have a couple of degrees in engineering. They are computer science degrees, but I still have a pretty solid grasp of mechanics.

Okay, at this point I feel like I have to invoke math because we seem to just be throwing empty words back and forth. Let's also take an extreme example to emphasize any difference that might be experienced: Oblivion (with it's eight across rows, has just be remodeled to have a zero-g.

Angular velocity for all seats is exactly the same because they're all rigidly attached. So is angular acceleration and angular jerk. Linear velocity, linear acceleration and linear jerk are are proportional to their angular counterparts by a factor directly proportional to the distance of the seat from the axis of rotation. Thus, the linear velocity, acceleration, and jerk of the outside seat should be about 4x as great (in the Oblivion example) as that of the inside seat.

If you take the example to the extreme with a row that's 50 seats wide. Going through a heartline spin would be insanely intense and whippy on the outer rows of the car.

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ApolloAndy said:
Linear velocity, linear acceleration and linear jerk are are proportional to their angular counterparts by a factor directly proportional to the distance of the seat from the axis of rotation.

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... Which is exactly what I've been saying since the middle of page 1 of this thread and you keep telling me is wrong ...

Somebody correct me if I am wrong, but everyone seems to be saying the same thing, but people thing others are talking about something else. Let me summarize the "theories" here:

On a B&M, there are 4 seats across a row, thus the following 3 statements would all apply to the zero-g roll.

1) All 4 seats traverse the zero-g roll in the same amount of time.
2) The two inner seats traverse the zero-g roll at the same exact speed. And likewise the two outside seats traverse the zero-g roll at the same exact speed.
3) However, the two inside seats will traverse at a slower speed than the two outside seats (because they have a longer distance to travel)

If anyone disagrees with any of those statements, then we have a difference of "theories". Otherwise, everyone agrees with each other, but are just expressing themselves differently.

(Side note: this is why I always like the outside rows on B&M's)

Sean
-Who has no semesters of engineering, but I did stay at a Holiday Inn last night-