Water park physics
February 14, 2015 12:44 PM   Subscribe

What happens if your group exceeds the weight limit on a slide at the water park?

On a recent visit, we rode a Tornado slide which had a combined weight limit of 320kgs. I think we exceeded it by 20kgs or so. Would we have gone faster, and travelled higher up the sides? (It felt like that). What's the worst case scenario if someone does significantly exceed the weight limit?
posted by dontjumplarry to Science & Nature (11 answers total) 2 users marked this as a favorite
I would hope that the declared max weight is significantly lower thaun the real engineering structural weight of the equipment. The one ride like that was if you could build up enough velocity you'd really just scrape along an edge. Perhaps some abrasion to arms or legs?
posted by sammyo at 12:49 PM on February 14, 2015 [2 favorites]

Response by poster: This is a really silly question, but according to Galileo shouldn't our velocity have been the same as a lighter group of four people (discounting air resistance)?
posted by dontjumplarry at 12:54 PM on February 14, 2015

It could be that a rider load that is too heavy will create too much drag and the slide won't perform as expected.
posted by JoeZydeco at 12:56 PM on February 14, 2015

Dontjump: at an equal speed, a heavier object takes more force to turn.
posted by SemiSalt at 1:01 PM on February 14, 2015 [1 favorite]

Semisalt: Yes, but in this case the turning is done by some combination of gravity and the normal force supplied by the surface of the slide, both of which are proportional to the weight of the person sliding.
posted by firechicago at 1:13 PM on February 14, 2015

You'll flatten the inflatable slide, bottom out, stop sliding and get stuck inside the ride.
posted by Cool Papa Bell at 1:19 PM on February 14, 2015 [2 favorites]

Yes, but in this case the turning is done by some combination of gravity and the normal force supplied by the surface of the slide

Unless of course, the slide couldn't provide that much normal force and failed. Of course, there's huge engineering margins on these things, so 20kg isn't going to do that.
posted by thegears at 1:21 PM on February 14, 2015

Not to be morbid, and this isn't going to happen if you slightly exceed the weight limit, but if you go totally overboard the whole slide could break and you'll all get seriously injured or killed.
posted by radioamy at 1:42 PM on February 14, 2015 [6 favorites]

A heavier group will keep more of their momentum through the turns and therefore more of their speed. It's the same reason why one of the ways that teams cheat in the bobsled is to add weight to the sled.

At some point, the tube would be so heavy that it would drag on the slide and counter-act that effect but I think you'd really need to overload the thing for that to happen. If you overloaded it to the point where it just barely still slid as well as if it had a normal weight, it could go so far up the side that it slide right over the lip. Depending on the angle, the tube would either tip over that edge and everyone would fall over the side or, if it's angled enough, they'd fall back inside the ride. It probably wouldn't be high enough to be lethal but might be high enough to cause serious injuries.

So yes, if your tube was heavier, you absolutely did go farther up the side than a tube with fewer and/or lighter people.
posted by VTX at 2:19 PM on February 14, 2015 [1 favorite]

It's a safety rating against injury, not a load-rating on the hardware.
posted by Sunburnt at 3:37 PM on February 14, 2015 [2 favorites]

As a general rule, things are built with a 25% to 50% safety margin. The more severe the potential injury, then the higher the safety margin.

Water slide is a potential fatality if critical failure occurs. My guess is that the sign says 300kg - but you do not start hitting real critical failure point until you reach 450kg.
posted by Flood at 5:53 AM on February 17, 2015

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