Yes it has happened, but is extremely rare, most fatalities are from drowning...

http://www.rideaccidents.com/water.html

http://www.livestrong.com/article/363624-water-slide-injuries/

http://amusementsafety.org/safety_news_08.asp

http://en.wikipedia.org/wiki/Waterslide

Or improper use, such as going head first resulting in a broken neck

Let me try....
(Thrusts with feet about 18 inches off center, sproings out over side wall.)
Whee!!
Thud.
(Reporting from final destination)--"Yup."

Please do try. The data would be invaluable.

What? Where's your responsibility, man?

This happened in Concord, CA maybe 10 years ago when a bunch of high school students ignored the lifeguard and all crowded onto the slide at the same time. It collapsed with the expected results.

About 12 years ago I was out in Las Vegas at a water park on the strip with one of those slides. Don't know if it is still open. Some kid was in front of me with the same level of intelligence I had at that age, 16 or so. The flume at the top of the slide had a bar across it with a warning painted on it, something to the effect of "stay seated." The bar was about six feet above the flume and right at the edge of the slide where it turns down. This kid took a couple of running steps and grabbed the bar and swung on it, using it to fling himself out over the edge. He dropped out of sight, and I couldn't see how far he free-fell before he contacted the flume again. But I could see he was off-center before he disappeared. I took my turn, and when I got stopped in the drag water at the bottom, he was struggling to get out. His back was sore, and he was limping. Within 30 seconds, a couple of security guards arrived, and walked him to a nearby gate and kicked him out. No medical attention, just get your butt out of here, kid. I don't think he was hurt seriously, just bumps and bruises. But who knows. Maybe he got a lawyer and sued them for his injuries. Bottom line, yeah, I think somebody could get killed doing that on a slide.

jhammond

If you fall off the side because you were fooling around by standing up then yes, and I have been there when it happened. Not pleasant I can tell you.

Slides are generally designed safe, but nothing is idiot-proof so accidents (freak or otherwise) do happen.

That's true. But as idiotic and fundamental as my question may seem at first glance, the reason I asked it is because of the tens of millions of people that have actually used them... and yet the number of "incidents" one can count on both hands. The percentage is phenomenally low. And when you consider the types of people that are the majority of users, foolish reckless teenagers and naive out of control children pumped full of adrenaline, it's simply amazing that these frightening rides have such an outstanding safety record. Evidently, considerable effort is required to injure yourself. The engineering of the basic premise of staying in contact with the slide at such heights, speeds and extreme angle must've been quite thoroughly worked out. But yet it seems that the safety envelope is continually being narrowed, as each park tries to out-do the rest; which in essence, I believe means they are slowly edging closer to the physical limits of safety. But still, even with this competition, the accident rate doesn't seem to have gone up.

As far as the straight slides go (which is the type I'm talking about in this thread), the only way to make them more thrilling is to go higher and steeper. I wonder how much higher & steeper they can go. From experience, I know that I barely touch the surface at times. I'm hydroplaning on a sheet of water. or even above the water at times.

So as far as that goes, why don't they just make it 200 feet tall, at the current angle of descent, and double the current highest slide? There must be a limit. No?

There would be a terminal velocity (~120mph?) on account of air resistance.

The slide must be designed so that it is always less steep than the corresponding slope of the natural parabolic trajectory.

Okay, so now we're getting somewhere.

Therefor, (and I don't know the angle of the highest straight slide), but if they were to double the height of the currently highest slide... they couldn't necessarily keep it at the same angle, because greater speeds would be reached (I'm assuming people don't approach terminal velocity on the tallest slides yet)... and greater speeds would mean less contact with the actual slide; resulting in less control and less safety. Is that correct?

The greater hazard to safety seems to be from heavier contact with the slide, rather than lighter.

I can't believe I'm giving you a GA for a post that contains the word Fart

The body's inertia may still contain a horizontal component, so just any angle will not suffice.

Wrong. There is no horizontal component to a body in free fall toward the center of the Earth.

The body is NOT in free fall on a radius to the earth's center; it still has horizontal momentum from the sloped upper surfaces of the slide.

Please retract your incorrect OT vote.

You obviously misread my post. With a perfectly vertical slide, there is no horizontal motion.

I did not discuss a "slope". Without a "slope" the body IS in free fall to the center of the Earth.

Have you never been on a slide which starts out in a tube with the floor falling away ?

We have them here in Florida. There is no horizontal component at first.

I don't think a vertical section of slide was mentioned until your very last post.

OK, this is from my post 13 you initially replied to:

...the slide would have to be virtually vertical...

You don't see anything here that resembles "vertical slide" ??

That does not address what the body was doing before the slide becomes "virtually" vertical, and what horizontal momentum it still may possess. (Which was addressed beforehand in the post mentioning parabolic trajectory.)

Breathing.

That is what the body was doing before the slide became vertical.

The bodies head was aimed perfectly away from the center of the Earth, and the "force" of breath had no horizontal component.

Then, without provocation, the floor of the slide disappeared and the body moved vertically toward the center of the Earth.

Most people here in Florida, when they realize they are in a slide where the bottom will fall out, scream straight up (not horizontally).

You are wrong since the movement is radial and the ea rth does rotate there is a coriolis acceleration which could be, depending on the slide plane, in the wrong direction and add to the hydrodynamic effect of the body sliding on the water layer.

Come on! How many Farts are horizontal?

The physics says that the slide would have to be virtually vertical for a body to move away from the slide.

Eh?!
The force of accelleration may be vertical but what about momentum?
If the slide suddenly changes gradieant in a downward dip you will loose contact.
Have you never been over a hump backed brodge?
Yeeee haaa.
Del

How much is this trajectory affected by vastly different body sizes.... say a 65 lb kid or a 280 lb used car salesman?

A person can fall to their death off anything, even a level floor.
Next!
Del

yes, depends on the position of the moment of inertia, good illustration.

I doubt a person could sit up while sliding down a ramp. He might be able to lift his head, but not his entire upper body.

Why not? Just put your hands behind your back and push... (It doesn't matter if you are sliding down or not. If you push, your body will be lifted.)

Deleted. My error. Didn't read closely enough!!

If a person decided to do that, then the process would probably proceed according to Darwin's theories...as it should.

But only once (probably)!

then aerodynamics takes effect, by getting air under you may be separated from the alide, especially more so with a body type as in post #47

Not that I'm saying that physique type is aerodynamic.

You are right if the feet stay so that a moment will be generated. In the sliding configuration this cannot occur.

Yes, this may not occur in a system without any friction. Let's consider this one:

Just leave a flagstone over a steep slope, standing on its narrow side, as in (a) (side view). Without any friction it should slide down as it is. But even with just a little friction, the flagstone -at first- will drop down to its wide side, (see (b)) and -afterwards- will start to slide down (see (c)). And even a waterslide have some friction.

However, I also believe that such a case for a human is really hard to happen (as it's shown in my post#27). I mean that the slope must be reeeally steep (i.e. almost vertical) or the man himself have to try a lot for this to happen.

Sorry guys. As a matter of fact, there is a mistake in my post#27. See the following image:

The supporting base is A (and not the black line depicted in the image of post#27). As far as the red line -arising from the center of his mass "a" and being perpendicular to the surface of the slide- is passing through his supporting base "A", the man should slide down normally (no matter how much steep the slide is, if there is no friction).

As you can see, -as far as the man is sitting down- it's rather impossible for the red line to pass outside the supporting base. (He should rather stand up on his feet in order to succeed to do such a thing.)

(In fact, what I've shown in post#27 should be true only in the case where the man's feet were bumped against an obstacle. In such a case, his supporting base should be the black line depicted in post#27.)

However, this is true in an ideal, frictionless system. In a real system, the friction will participate and it could result to the overturning of the man, even if the red line is still passing through his supporting base. (See my post #64). Nonetheless, I still think that this is difficult to happen... Probably it could happen in the case of a very steep slope and sufficient friction...

HELP! I was just trying to prove a point, and something went totally wrong!

Terminal velocity on a 200 foot slide could be much greater than 120 mph. Downhill skiers can break this limit. If you jump out of an airplane wearing a wet suit and fall feet first, what is your terminal velocity? As far as I know the 120 mph mark is the SLOWEST a person can fall.

-A-

Also depends upon the aspect ratio (height/circumference) of the person. People of low aspect ratio, i.e. approaching unity, can be modeled as spheres.

jhammond

It is the rate of change that does the damage, not the highest velocity. So even if you are away from the slide, in free air, for 200ft, if the slide scoops you near the end of the fall, and you decellerate over...what, as little as 5 seconds, I would say you are safe.

Falling 90 feet onto water, no, i would say you are not safe.

cnc jim

Certainly falling ONTO water would not be safe, unless one could sink INTO the water (i.e., the water is sufficiently deep to allow safe deceleration without hitting bottom). Witness the abilities of tower and platform divers, who do it from much higher distances, and the survival of military sailors who have fallen/been blown/jumped off the decks of Aircraft Carriers, many of which are more than 90 feet above the water.

Of course, that is not to say that a bad entry (one can only imagine how bad a "belly whopper" or "belly flop" would be from that height. Indeed, it makes MY head ache just thinking about a head-first entry at that velocity) is survivable, but properly executed, an entry from that altitude need not even cause bruising or undue stress on the rider.

It is, indeed, the rate of change that matters most. And falling vertically from any height is no problem, as long as the proper length of time and distance traveled are a part of the vector conversion process.

When I was a kid, in then Mountains of California, we used to jump our toboggans off of a rocky outcrop about 40 feet above the bottom of our run. Only once did one of us try to continue the "flight" out to the flat, before landing. Before and after that, we ALL went for a face-of-the-run touchdown. That flat landing HURT, even landing in 4 foot deep snow!

Right. We're getting off track. I'm not talking about the safety of these slides when everything and everyone works as supposed to (i.e. maintaining the perfect ankles crossed, arms across chest, keeping body straight). I mean, while you are falling that distance, and you are possibly away from the slide... is it not simple enough to do something stupid during a panic, or to goof around, and inadvertently increase your trajectory beyond that which is ideal, and not have the opportunity to be "scooped" at the end... but instead hit a portion that is horizontal at the bottom.

Or is this scenario very difficult to do, even if one was to try?

Again, I call attention to the tens of millions of rides that have been taken on these things, by such a wide variety of hyped-up people, and yet the accident rate is incredibly low. So aside from a structure collapsing, I was wondering if the physics of the situation simply made it "virtually impossible" to fly off these straight steep slides once you start sliding, despite what you do on the way down.

I get you now: To paraphrase:

These slides look dangerous. How come more people aren't killed on them?

cnc jim

Yeah, that's pretty much it.

Ah! Excellent, on-point answer! Exactly the info I was looking for.

Rate it a good answer then - don't be mean. Who on earth voted that as Off Topic???

Cnc Jim

Don't be mean? Why are you presuming I didn't give a GA? I said I was. As far as my reasons for starting this thread, it was the most useful answer to me so far.

Someone with an immaturity problem is evidently throwing around OT's in this and several other threads, canceling quite a number of well deserved and obvious GA's.

Most likely the same kind of person who posts as Anonymous. Although the Anonymous option might have one or two legitimate uses, personally I believe its misuse has more negative impact than any possible positive impact.

because your using ratios which would make it more of a slope diagram and not a force vector diagram.

And your would need approx. 205# to keep you in equilibrium

Can you explain what you mean by that? Why are his ratio's incorrect?

this statement here,

If the angle of incline is even 9 degrees from the vertical, there would be a 20 pound force pushing a 200 pound body (9 degrees is 10 % of the total vectored force, since 9 degrees is 10% of the total available angle from horizontal to vertical.

Basically this is what threw me off by calling it a vector force, degrees of angles are not proportionate.

So I actually drew a force vector diagram along side a slope diagram to show the difference, by using proportions with the percentage such as 10% of 200. Using the 10% as stated, one would come up with about 6 degrees and at 6 degrees the force would be about with a 10% slope ratio

atan (0.10) = 5.7 degrees or approx 6 degrees, not 9 degrees.

Understand?

Okay. Makes sense. So in one sense, it's less safe than micahd proposed.

yes, its even worse if you take into account the offset of the moment of enertia of your subject away from the slide especially with this type of problem.

(The problem being his physique, not whats he's holding in his hand, thats another thread)

There is a typo on the slope diagram, its supposed to be 1 not .1

Yep. I see my error. And you are much more accurate in your math. OTOH, a force vector is still appropriate, since the force of gravity on a sloping face IS made up of proportional force vectors.

And I still don't think most of us could, merely by waving our arms, no matter how vigorously, launch even the 5 pounds you calculate through the same 7.5 feet (conservative estimate. Look again at the details of my assumptions) of forward travel.

yes, when you suggesting force vector is what started it.

And I still don't think most of us could, merely by waving our arms,

don't underestimate momentum, plus, once you start getting air between you and the slide, you basically loose the little control you have.

Also, these slides do have varying lengths of horizontal slide at the very top, in the staging area. So there is some "launching" effect right from the start, depending on what speed is achieved in those first few feet, or if they push themselves off. So I believe you lose contact with slide almost immediately and are in free fall, and at some point catch up to the curve, depending on your launch speed.

I think it's the first second or two, that might be the greatest "thrill" and danger, despite the fact that it isn't the greatest velocity of the trip. By the time you gain speed, I think you are back in contact and halfway down.

After casting about on Google for a while the fastest water-slide I was able to find gets folks up to 35 mph.

I can find no direct indication of actual angle of slide. The words "near vertical" are used allot. This appears to be a GROSS OVERSTATEMENT.

A vertical drop of 200 feet will get you up to about 75 mph. (Feet first with wind resistance, estimated)

I think fear and camera angle have more to do with the perception that these slides are "near vertical" than anyone until now has estimated.

I have no more time for this matter, but I think we will find that the slopes are less than 2/3 vertical, (ie 60 deg).

-A-

Thanx for doing the math on the top speed. But, I do believe you have the angle wrong though. I'm pretty sure that 60mph+ is reached, and I don't need a camera angle to see in person, that the angles are closer to 80. It's in my blood. When I see structures, I'm going to examine them even if I'm just standing in line.

Don't think you'll find me standing in line at an 80 degree slide.

In order to free fall at the beginning portion, it must be considerably steeper than 60 degrees. And to reach 60mph, it also must be considerably more than 60 degrees. Yes it is amazing that no one gets injured by losing control and losing contact. That's why I'm bringing it up in this thread.

Good answer. Better than any engineering treatise on the subject, including mine.

Never underestimate the power of a desire to live. But also never underestimate the power of the public to be stupid. Hence the few who DO fall off of these things, in BOTH cases!

I agree. GA.

enough is enough.........stand back, everybody.

I'm settling this once and for all.

I remember reading about some guy actually doing this with a pair of specially designed skates. Now THAT seems like it would up the stats some, no?

stop pushing......I'll go when I'm ready..... Stop Pushing I say!

LOL !