How is a Manu Bomb So Powerful?
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- Опубліковано 10 лют 2025
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I show you how a Manu, or water bomb creates a water jet (Worthington jet) that is so powerful it can send a ball shooting into the sky.
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"Did you need the electromagnet to drop the metal ball?"
ActionLab: "Yes"
It helps. Keeps it only going straight down.
I realise he used it for good reason, but those were still my initial thoughts, too. :D
"How does one create a large splash of water? Well, it's quite simple, really. Let me juuust get my electro magnet..."
Was hoping for a coil gun
@@diggaaa13 My thought process was exactly the same!!
🧾☑️
There is nothing I love more than the Manu getting the international attention it deserves.
Manu Ginobili
I agree!
It didn't. It got appropriated and was renamed Worthington jet.
I never knew that the Manu was a thing. I've been doing them for about 35 years, made it up when I was a teenager. I've always amazed all my friends and family at how big of a splash I could make.
Hold a water bottle while jumping in letting it go in the water
Same story! My siblings and cousins called them butt bombs. It started out as kicking out of a cannon ball, and then you would to try to “kick” water at people on the side of the pool!
@@joebovovitch7803 we’d do that with soccer balls! Buoyancy can store a ton of energy too!
You should’ve patented it! Jk
We called the jump a "watermelon." Never did it with and object to launch though. It's pretty cool
When I was growing up we had two things we did from the high board (3 meter). One was a "cannon ball" which was the same principle as the steel ball. The chubby kids were really good with a cannonball. It also was a way for kids who didn't know how to control their position in mid air to really hurt their backs. The other was a "can opener". This, was a far more effective splash for people that actually knew how to do it. It is basically the same as the "manu". The trick is to lean back as you enter the water. Instead of grabbing your knee at the height of your jump, you wait until just before you reach the water. By bringing one knee up towards your torso your body begins to rotate backwards. Your extended foot pierces the water so that as you flatten your back, the water doesn't slap it as it would in a belly flop. If timed just right you could soak the lifeguard sitting 30 feet away and 10 feet in the air. The most addicting thing about doing this is the intense concussion of water you feel as the bubble collapses around you. A good can-opener rattles your head. You know you did it right if your body abruptly and completely stops moving down through the water just a couple of feet below the surface. You actually hear the concussion like an underwater bomb. "sssSSS-BOOM"
I used to do can openers too the other we would do we called a sleeper, but it's basically manu. We called it the sleeper because it looks like you are sleeping in a recliner as you hit the water then tilt back to make the splash effect
As a kid I did the can opener but didn't have a name for it, other than bomb. You know you've done it right when you hear and feel the ka-boom. It gives more consistent results than a belly flop or legs tucked in.
what the poor lifeguard do
Yep, can opener and cannon-ball were two classics. Another was "the preacher" or "preacher's seat" which seems to exactly be the "manu." The biggier, heavier kids were always better at making huge splashes because they were obviously displacing more water. I used to do another dive where you'd fold yourself into a U shape and let your hands and feet go into the water first, then after your belly hit you sort of turned the U inside out and it would make a nice splash...can't recall the name of such a dive.
@@mitchd949 I was on the diving team most of my teen years. The "U"dive you describe was a "throw-away" or an intentional "fail dive". If you were in competition with another team and found yourself ridiculously ahead in points, you would do this on a dive you normally didn't score well on to sort of even the competition. We called it the "duh dive". Because your feet and hands enter the water at the same time it can't possibly be counted as any type of legitimate dive, and get's scored '0' points. In this case you didn't try to make a big splash - if you got the judges wet they tended to score lower on your remaining dives.
Interesting. At the pool we would always do a "cannon ball" and make a big splash. But the biggest splash was made by a "can opener". I would jump in feet first, tuck one knee in, and on impact lean back to hear a loud "boom". That's when I knew the splash was really high. Knowing how to control it allowed you to direct it and... make the lifeguard wet.
We used to see who could hit the ceiling of the YMCA the hardest with water. I couldn’t remember the name of it.
Tf is can opener
I thought the name "can opener" was only used in Memphis. The more I know...
When he described the Manu, I couldn't help but think the technique is the inverse of the can opener. Then I thought about the "swan bomb". You start off with a swan dive and tuck into a ball, head first into the water. That make a bigger splash than the can opener if you do it right.
@@SlinkyD What you call a swan bomb we called suicides
@@happyman6102 Our suicides was a regular dive where you put your hands on your hips and did like a 45° bend like doing a jacknife before you entered. It was more of a psychological challenge. Bigger stakes when you do it near the bank in the 3".
I just realized danger and elegance was a big part of our swimming style in the hood.
We did these at the public pool. There's two versions. The can opener, which is a cannonball holding one knee only and keeping one leg straight out in front. You have to hit the surface tilted back at about forty degrees. The second was the chair. After springing off the board you a assumed the back lean like the can opener but froze in a seated position with your arms tucked into your sides with your palms covering your eyes. Getting the angle right doesn't take long. You know you did it right when you hear the tremendous thump of the water cavity collapsing underwater.
My friend taught me the can opener. He mentioned to grab your knee and crank backwards with your whole body. In that way, vert similar to what was described in the video.
gotta love a person who can explain science so well, thank you. you make it very easy to understand.
Cringe Af 😂
@@Lamiishere no
We need meth
@@Lamiishere shut up normie
@@Lamiishere 🤔 why tho?
Since I was a young boy I’ve done a similar jump called the ‘can opener’ wherein one knee is pulled up to the chest but same body-back motion as the manu. Always gets a huge water jet!
You've just solved an old childhood mystery. My brothers and I would have "highest splash" contests, and sometimes we'd generate HUGE splashes seemingly at random. None of us were able to narrow down exactly what we were doing to make them.
Cool
Just learned about this. Gotta love when things come full circle.
That should be an Olympic sport. I would watch it.
Whatching education content more and more and you’ll find all the secrets to life 😉
And you've gotten nowhere closer with this failure in backyard tinkering/repeating.
I just realized during your ball drop experiment that this is a great analogy for what happens during a lightning strike. The initial bolt rips the air apart and creates a cavity in the atmosphere, and when it slams back shut, the "jet" of air it creates is perceived as thunder.
I wonder if a literal jet of air is created in the upper atmosphere and if this could have anything to do with sprites, jets and elves (the atmospheric anomalies, not the creatures).
That's not accurate.
@@ObservationofLimits Please elaborate
@@joho0 I think what you're hearing with thunder is the actual expansion shockwave from the superheated air. Inside the lightning bolt you have high temperature AND pressure. Both components influence the sound effect. On a side note, that high temp/pressure is why NOx is formed naturally from lightning. There is some amount of collapsing air that does get transformed into sound, but that pales in energy compared to the expansion wave. Maybe you could hear it if not for the expansion wave itself (crack) combined with the late arrival of the expansion wave from the upper portions of the bolt (rumble).
I don't know what causes sprites, jets, or elves, but my guess is the physics of lightning change at high altitude because you have lower temperature, air pressure, CO2, and H2O gas constituents the higher you go.
I use to Manu bomb as a kid all the time. My technic was to jump in like you're sitting on a chair, slightly laid back, then when submerged in the water flatten out such that you make a bigger hole for the resulting upward rush for the splash. If you do it correctly, the splash should sound like a loud thud from the shock wave (especially in a pool). This bomb technic is a very Kiwi thing, especially among Maori children.
We did the same thing but also used to pull one knee to the chest that way we were automatically rolling backwards as soon as we hit the the water. Fun times
Aloha! Here in Hawai’i manu bombing is popular as well. I had no idea it was invented in New Zealand. Do you have any more info of who originated the bomb?
Children have presumably been trying to make big splashes since the time we lived in caves. The practice probably got perfected in communities that didn't have access to things like Gameboys and PlayStations until much much later.
@@donovansun5470 Probably a guy called "Manu", it's a Samoan word/name.
@@Bishop0178 In the midwest of the United States we call that the 'Can Opener!' Great for getting the lifeguard on duty at the pool soaked.
I worked as a lifeguard in a pool for quite a few years and we were always messing about doing "Bombs" from various diving boards to see who could make the largest splash. Its interesting to see the actual physics behind it.
The Slow Mo Guys did an amazing experiment inside a wave simulator that has complete round basin that can generate waves from all sides, and they do this, not by dropping in a round object, but to crash precise waves into the center, giving the same effect of a very high jet.
A rogue wave!
Yes exactly, I was thinking I saw this before somewhere there you go!
A bomb that goes a bit higher than a manu is an easy one called the coffin, you jump in feet first but as soon as your feet touch the water you lean back as fast as you can
I’ve enjoyed your videos for years and you have inspired several useful inventions I’ve made. Thank you for all you do!
thank you!
@@TheActionLab why are galaxies in a disc instead of a sphere?
@@jonathanperry8331 May be because they are spinning. If you imagine multiple balls connected to the end of a rod which spins, they would form a disc like structure.
@@pinakadhara7650 well I guess that's the big mystery is what is the rod? We don't really understand gravity yet but what's holding all of this together? You have your dark matter theory and the maybe there's a black hole at the center of the Galaxy. I hope they figure this out in my lifetime but I kind of doubt it.
In order for material to stay in orbit, the momentum trying to go strait has to balance with the force of gravity pushing it to center. This only works if the material is rotating about the center of the gravitational pull. To understand this, imagine a spherical galaxy. As it spins along an axis, there will be stars spinning at the top of the sphere close to the axis. The inertia will be pushing the stars away from the axis, but not away from the center of the sphere, but gravity would pull towards the center of the sphere. This would make the stars “fall” towards the equator of the galaxy, where they would collide with stuff and either fall towards center or fall into orbit around the equator
One thing I love about Action Lab is you never know what new topic it’s going to cover. It’s almost always something fascinating that I didn’t know was a thing. And, of course, explained so the physics can be grasped by a non-physicist.
I can remember as a kid growing up my family would visit the Okere Falls near Rotoiti (New Zealand) and there is a place here that all the locals used to jump of a high cliff into the river below where the water was very deep. I took a lot to build the courage to jump this height and at this height you made sure you kept your body straight and upright and hit the water feet first. I can remember one day seeing a group of local Maori teenagers who decided to manu from this jump height.
You kinda left us hanging there.
@@johnloosemore9949 he left us "jumping"
So how far up did the splash water travel then?
@@YTho-ev1ej my favourite summer pastime 😂 The water is always freezing tho so can’t wait for it to get a lil warmer lol
@@johannesaskehov The splash of their souls traveled straight up to heaven
As a kid (now 56) my friends and I would do what is called a "jackknife" from the high dive and could aim our splash.....usually at the lifeguard on duty! Same principle, hit the water with your body at about a 45* angle with one leg bent up towards your abdomen held by your hands and when your foot touches the water you quickly lean back to create the same motion and effect as mentioned in this video. Good explanation of what my 12y/o self did so many years ago. Even if the science behind it didn't matter to me before, it brought back a lot of forgotten memories of being young and having some innocent fun. Good video!
We used to call it a "Can Opener" The only difference is you grab one knee and pull it tight against your chest while leaving the other leg extended, once your foot of the extended leg touches the water, you wold lean back and continue to fall into the water at an angle. . I remember how it would sound underwater. I never really thought about it but now I know that the sound it created was the void cavatating.
Yep, that's the way I remember it.
I remember that one, but my favorite was the "watermelon." It starts like a swan dive but you tuck and roll just before hitting the water. Watching this video, I realized the common action is using your back to make the biggest void without just landing flat. Maybe I just wasn't very good at the can opener and cannon ball, but I could do the watermelon well and it looks crazy. It also gets your head close to the collapsing void to make that part more intense.
YEAH can opener
When I learned the can opener it was all I wanted to do. No one beat me in splash competitions ever again.
In germany jumping in like that is called 'Arschbombe', literally ass-bomb 😉
This seems closely related to how a shaped charge explosive can penetrate crazy thicknesses of steel plate. It always amazes me how a relatively small diameter hole can keep going and going through a couple feet (or more) of steel, without even "mushrooming" out and dissipating.
I was about to coment this, the way the cavity closes and creates a jet by pinching the material is surprisingly simmilar
I'm amazed he hit the falling ball with the up-shooting water.
Noone talks about it in comments but that is some next level timing and throw + jump coordination damn
@jimmy Burnett I throw the ball and jump: ball goes next door. I land in the sand for some reason.
... NAILED IT!!!
We called it a jackknife, one leg straight the other bent, holding it with your arms, as you enter the water foot first you pivot backwards creating a larger cavity. We used to see who could hit the ceiling of the dock (about 20’ high) by jumping into an empty houseboat slip. Most of us could easily hit the ceiling.
A family friend that used to watch us as kids taught me how to do this and I used to do it all the time. We would just hold onto the ball, not throw it. I also did it all the time with no ball just for the splash. You always knew when you did it perfectly by the sound it made under water, and when there was a bunch of pissed off people when you came up. I never knew it had a name until now.
2:37 funny enough a HEAT round from a tank or RPG works somewhat similar to this, just instead of water collapsing back together its an explosive forcing a copper lining into one point. Both things concentrate all the energy into a single point to create an extremely fast jet simply due to the geometry
I don't know how you do it... Every video you release is just so interesting and educational. Love it!!
Oh, I know: he goes to the point.
Always done this as a youngling in NZ, although we just called it a "bomb" and the act of doing it "bombing", never heard it referred to as a "manu".
We used empty coke bottles instead of a rugby ball also.
I didnt knew that was called a Manu! Sometime in my teenage years i found out you can make a really big splash if you land "sitting" with your legs straight out, and as you hit the water, lay flat fast. Now i know why, thanks!
For the most repeatable and forgiving setup, I hit in a tight V and almost immediately try to flatten out, like an backwards parachute. Just trying to slow down as quickly as possible while also entering the water as smoothly as possible.
I've done it as a dive while touching my toes and got huge results, but there was less room for error
This also perfectly explains the toilet splashback bidet effect.
Nice work!
There is a Smarter Every Day video covering this exact thing.
In Oz as a kid we did this as well never called it a Manu it was called the Jerry bomb but I always got a way bigger splash from doing what was called a "Horsie" . Same principle but in reverse, as you're falling you have your stomach pushed forward with your back arched backwards with arms and legs in a parachute free falling position and just before hitting the water you flex in the opposite direction, have your arms and legs hit the water 1st and just as your torso breaks the water, flex your stomach forward again so there is hopefully a pocket of air that is now being compressed even hard into the water. Same principle as having your hand flat and making a splash or cupping your hand and then flattening it out as you hit the water.
This looks very similar to the Munroe effect that is used in high-explosive-anti-tank ("HEAT") warheads (hollow charges) to create a very focused and high velocity stream of molten metal to penetrate a tank's armor.
It's literally the same thing happening. Ofcourse with much lower velocities
It is actually the heat from the plasma jet that cuts the hole in the armor, the molten copper cone follows after and can go through the hole, but sometimes gets stuck in the hole. I saw pieces of armor punctured by shaped charges at Aberdeen Proving Ground. Some of the armor plates had the once molten cone wedged inside the hole, looked somewhat like a copper icicle. But unlike the manu bomb the energy comes from the high explosive, not the cone used to shape the explosive or anything surrounding the charge.
@@OnTheRiver66 bs. The cone is a superheated jet of copper that goes so fast it just pushes the armoe out of the way. This is a fact.
@@KClO3 then why do some of the armor plates have the cooled copper cone stuck half in and half out of the hole? That cannot happen if the molten copper first made the hole - the plasma moves many times faster than the copper and is gone before the copper hits the hole. I received my training at Aberdeen Proving Ground as an Ordnance officer and I know that copper as well as other materials are used to hold the cavity shape in the explosive just long enough for the plasma jet to form during detonation. Copper works well and that is the only reason it is usually used. Where did you train?
I also later worked for a company that made a product that significantly reduced some of the force of shaped charges and that product had nothing to do with the copper liner but interacted with the high temperature plasma from the explosive itself.
Similar to a manu, as a kid we used to do a "jackknife". You'd jump into the water while holding 1 knee and your other leg extended. As you entered the water, you'd fall backwards letting your extended leg rise above the rest of your body. Made for great splashes. Holding your knee helped to lean back farther and faster for larger splashes.
This explains something that I was intrigued by when I was a kid. Growing up in the tropics, a lot of time was spent staring at the rain drops, and each drop used to throw a larger jet of water into the air as it hit the puddle - I think this is the reason behind that. Thank you!
I grew up in the tropics as well. But didn't spend anytime staring at raindrops falling on puddles.
But I still live in the tropics. Never too late to start. 😁
@@danielch6662 Southern Indian houses that I lived in had a "verandah" in front, and it was a pleasure to sit outside watching raindrops (except during lightning storms)
Finally someone that isn’t from a pacific island and isn’t a Pacific Islander knows what a manu is 😭
I’ve known how to manu since I was young, and growing up in hawai’i we would go to the waikiki walls and practice
Even a single piece of toilet tissue laid in the toilet bowl can prevent all undesired splash back from reaching your fundament. The water surface of toilet bowls is small and the depth often shallow so after the first impact, any subsequent stool that goes into freefall is likely to interact with earlier deposits preventing any subsequent jets.
No one else (of the admittedly few) with whom I've discussed this has done it so this doesn't appear to be a widespread technique amongst people I know and I am inordinately proud of making this discovery myself. Yet there is a German language term for it translating to "building a raft". It doesn't take a raft though, one square works perfectly and is just that little bit more environmentally and economically friendly.
I'm sure others have made their own independent discoveries like me, but it can be a rather awkward thing to share. Maybe someone out there is brave enough to start a social movement about this movement.
I only learnt about this technique a year ago and it has changed my life 😂
but I love feeling that jet pierce into my butthole, cleaning me both in and out ykno.
Destin from smartereveryday did a video on poop splash a while ago
"Inordinately proud of discovering this myself" you must be German 😂 that, and "fundament" is a rather German turn of phrase to my linguistically trained ear lol. I truly must use that.
@@iteragami5078 of COURSE he did lmao. How could he not? The collapse of the water column is so smooth and _laminar_
I used to do this all the time as a kid growing up in the 80s. I called it the jackknife, because I would grab one leg with my arm, and jump in a bent position. As soon as I hit the water I would straighten the leg up and lean back. It caused overpressure which launched a splash straight up - usually. I got good at aiming it and I could actually control the direction - somewhat - it would fly. So I could splash people sitting on the deck :D Everyone thinking they were cool doing the cannon ball, and I could launch a splash 20 feet into the air :D I remember you knew when you got the sweet spot. You could feel the vacuum under you, and the water rushing up. You kind of "fell" into the hole from the water. It made this "whomp whomp" sound, with the second whomp usually louder and more forceful than the first. It was a very unique feeling that is hard to describe. If you did it you know it though.
U make science so easy to understand
When I was a kid, I was the master of creating a huge splash of water. We always did it from the high dive in an attempt to soak the lifegaurd. When I was a kid, I always called them a "Sleeper" because of when laying back right after entry into the water. Never knew they were actually called a Manu. I was doing this nearly 45-50 years ago!
This should have been called the toilet water jet.
I’m taking a shit reading this
Poseidon's kiss
AKA Neptunes kiss
Oh man, now I know.
Just put toilet paper in the water before you take a dump and problem solved 😂😂😂😂😂
I don't think I've even been following James that long, probably a bit over a year, but it seems like the channel has grown MASSIVELY. I don't remember seeing his views go into the tens of millions per video back then! Maybe they were, but either way I'm very happy for his success.
We called it the coffin, arms crossed, feet first and then as feet enter the water your body, slightly bent, overtakes your feet thereby creating the large cavity mentioned.
Also it can cause, if done right, quite a clap noise when the water collapses back.
We were quickly banned from doing that due to the noise and the wet ceiling, haha, great fun though, thanks for explaining the mechanics behind it 🙂
A coffin and a manu are completely different
@@999nevamind They look remarkably similar to me, the way the guy entered the water, only difference seems to be the arm crossing.
@@antitheist9976 no, a coffin you basically stay straight, you have to tuck for a manu and then roll out once you get into the water
@@999nevamind Where I am from, when jumping into the water whilst making the splash and the cavity that causes it, we called it the coffin, due to the crossing of the arms.
bro how to say you went swimming but never actually went swimming without telling us you cant swim
I'm really good at manu you named it. But we call it "panu row"
, You just need to lay down and cross your feet together and it will make higher splash.
Mesmerizing. Very cool to see the close up details, fluid dynamics are wild
On another note, this is probably why canonballs in naval warfare were quite effective for a long time even if they do not hit the target itself and only lands somewhere near, because then then other than the manu bomb effect, when the water fills up the cavity of impact, it also pulls water from its surroundings disturbing the area where the target is and possibly capsizing it if enough disturbance was made. Now, of course, everyone has deadly missiles.
Fascinating. I'd never thought of that, but it sounds legitimate. I'm very glad that my local swimming pool has banned cannonballs and missiles, as my galleon has sprung a leak. ;)
Amazing physics! I never heard of this Manu but looks like fun!
I did a manu once unintentionally once at the public pool while doing a can opener off the high dive. I went what felt like 6 feet deep before the water actually started closing above me, and the splash was enormous. I could never quite figure out how to do it again on purpose, so it was really cool to learn that other people have mastered it!
It’s like a shape charge of water
Haven't heard "Shape Charge" in awhile.
Combat engineer?
That's a good analogy. What I'm wondering is why did he need the electromagnet? He could have just dropped it.
@@jonathanperry8331 I'd say he wanted to keep every drop consistent and straight
@jonathan Perry because he’s next level smart.
My older brother went to a "sports school" in the late 70's, which was actually a camp for troubled kids in Whangarei, New Zealand. Him and a group of his friends would go to Whangarei Falls, a local swimming hole and have competitions to see who could create the biggest splash. They developed many different techniques for creating a "Bomb" the most successful being the one mentioned in this video. The name of that school was Maunu Health Camp.
You just explained Poseidon's kiss without having to mention it. 😂
I'm from Hawaii, and this has been a strong part of our culture for generations! Me, my father, his father, and back and back and back. Here we call it "bombing". This particular maneuver is called the "suicide". There's are also different variations of bombs like the "watermelon" and "manu". During summer vacation or on the weekends you'll see a dozen kids standing on rocks or piers like Waikiki Walls, Waimea Bay, or Zablans taking turns jumping from sunrise till sunset. All of them competing to make the biggest splash, or to see who can "pop" a bottle or ball the highest using the pressure of their splash (its hard to explain). Love seeing how it's called different things around the world.
zablan? come on brah you didnt have to say that one, it shouldnt even qualify as cliff or rock diving. Its just a small leap.
@@house_greyjoy eh you still see fakas bombing the caves tho 😂😂
A similar jet effect is used for injections without a syringe. The jet of fluid is so fast that it penetrates the skin without requiring a needle. In that case the jet is created by quickly heating water in a cylinder, similar to ink-jet printer nozzles.
And with copper in anti-tank munitions I believe.
Can we get this jet if we are hit by something big and spherical like for example the asteroid that killed the dinosaurs? 🤔
A few days after watching this video, I made a smoothie that was a little too stiff and had an air bubble in the bottom. I hit the bottom and the bubble popped, leaving a funnel shape to the bottom of the cup. Not thinking, I hit it again. I got about five feet of travel and a purple mess on the wall. It was then I realized what I just did. Thank you.
I've seen others mention it so my vote is for the "Can Opener". But part of the skill was controlling the spray. While sometimes for height, also to spray people standing around the pool. You could get some distance to the back row lounges!
And I found a properly performed "belly flop" did not hurt and made a great side splash.
We used to call it the "can opener." Whenever we'd go to the pool and people were talking turns on the diving board, and someone pulled out a can of tuna (back then they didn't have the pull tabs) and looked at each friend imploringly when one finally pulled out a metal scissor-esque device, that was a can opener.
We used to call this a "cannon ball".
We had a couple of techniques that we called the “can opener” and the “coffin.” Both were similar to the Manu. We would jump in butt downwards, then force our back into the water at the right moment. If we did them correctly, we created huge splashes. When we would swim in indoor pools, we would try and see who could get the most water into the ceiling. We also had a belly down splash maker called the “Fuji.” It was almost as impressive as the others.
I don't think this was ever a thing in boring Britain, particularly in the seventies and eighties. All our swimming pools famously had signs up that said "No bombing" with a picture of a boy curled up like a ball. They also said "No petting" which always made me laugh. There was nothing to say you couldn't pee in the pool though, so that's what British kids did to amuse themselves.
Crazy that no one ever jumped in the water until someone From New Zealand did it.
What I’ve learned here today is that I need to oil myself up before I do any bombs/manu xD
4:06 Taco Bell ...
We jump in similar way and we call it bomb, but instead of spreading out, you stay curled up to create bigger cavity.
One disadvantage is that your head is on top and cavity can colapse on your head with quite a concusive force, but it's realy something special to hear.
I have only known it as a water bomb and it was already well known how to do it when I first learnt and started doing it in the early 70's here in Melbourne Australia!
I'm surprised to hear that it was invented in New Zealand..... No date was given as to when it was discovered?
The video shows the guy going in backwards, we also could achieve it going in forwards which I believe produced better results, you could actually aim where you wanted the water to end up, the girls unfortunately didn't find it as amusing as we did but it did get their attention! They would always make sure that they knew where you are at all times LoL.... One deliberate splash, lots of apologies and eventually a date.
In my youth, we called it a “can opener”. It was the same theory, but, the person would cradle one knee with both hands as the water was entered. With practice, the jet of water could be directed at a modest angle. Innocent and dry sun bathers could be soaked from a distance. What fun!
the first time I heard about Manu Bomb. In my childhood we had several types of water bombs.
- Brett (board) (very similar to Manu Bomb)
- Totenbein (dead leg) (one leg stretched, the other pulled to the chest)
- Kopfbombe (head bomb) (as vertical as possible, head first and roll in just before touching the water)
- Schwalbe (Swallow) (as horizontal as possible, belly first, just before touching the water pull in arms and leg and then stretch back through)
I didn't know what me and my brother were doing has kids was essentially a Manu Bomb. We just called it a "Can Opener". Only difference is we grab one knee with both our hands while the other leg stayed straight. Releasing on impact to achieve that rapid opening of the body. Thanks for showing us he science behind it.
this is really important science - we need to minimize those Worthington jets in toilet bowls
It is a phenomena that has been studied intensely for a very long time. Anytime an object can displace the water then the air bubble that follows the displacement will collapse behind the displacement and shoot upwards. The reason this is so interesting is that people would normally suspect the shooting of the water upwards would not be so extreme. Even engineers are often surprised by this. It actually shoots up at a speed something like twice the velocity of the object entering. (remember it is smaller in mass than the object) In a related problem, suppose you take a large rocket and shoot it out of a sub, (as in the Poseidon missile.) These rockets were being shot out of a sub back in the 60's with a big blast of compressed air. The plan was for the missile to exit and as it was leaving the launch tube, it was ignited, (so that by the time it got to the surface, say 60 or 100 feet, it was ready to fly upwards) But if anyone might still remember, often the missile would fail to ignite. Quite a costly problem. My father was a physicist that worked for Lockheed at the time and he was called in to try and figure out what the problem was. He realized that the problem was basically this same effect. The rocket, (I think it was something like 6' or even 8' in diameter, was pushed from the sub with a large volume of air. As it left the sub, the air bubble behind it would eventually of course collapse, (no longer being a column of air connected to the sub) and the water rushing in would basically produce this same "manu" effect. It would shoot a column of water up from the bottom of the bubble, straight up the bubble trailing the rocket ascending to the surface. Surprise! this column of water was about 1' in diameter and shot up at about twice the velocity of the rocket. These rockets were solid fuels as I understand and basically the ignited surface was in the center of the rocket. Obviously a "fire" doesn't really like to be hit by a 1' diameter blast of water on it while it is just starting to go! My father, figured that out and proposed a solution, a baffle that would deflect the water blast, but that would be blasted out of the way once the rocket engine got going.
I am 66 years old. We did this as kids in Texas and we called them Can Openers. The key was to cover your face with both hands otherwise it made your face really sting - like a slap to your entire face at once. This not only made a higher splash but done right you could throw the splash in any direction you faced away from. Much better than Cannonballs!
In Australia as a teenager we call this the lay back. Jump bring 1 knee up then lay back just as you hit the water. Splash everything above. You feel a shock wave like double thump threw the head & shoulder. Small thump when opening the cavity then larger one when it closes. I didn't really think about the science behind it till now Thankyou
The pressure & momentum of the water entering the cavity that was caused by the man that jumped in the water produces a vertical splash that launches the ball up.
the concept seemed pretty intuitive to me because i often play around with water (anything physics-y) during my swim practice, and i kinda just learned how water behaves in certain conditions
This is the way many sea-mines work. The explosion is not there to crack the hull by itself but to create a cavity that shoots a massive column of water with a very good portion of the bomb energy. This effect concentrates the energy into one big hull busting water jet.
ive been making splashes like this since i was a kid and had no idea they had a name or a backstory like this. we called them can openers and just learned than if you hit the water the right way you get a huge splash. cool to learn all of this years now as an adult
The difference between a 'can opener' and a 'pike', is that one leg is extended for a can opener and both legs are extended for a pike. Pike's always make a bigger splash if executed properly. The key difference is that I have both legs available to lever my back into the water when I make entry.
I enter the water legs first at ~20deg, with body almost vertical(say 130 deg from legs). When my legs are fully submerged, I push hard down on my back using my hips as a lever and use the water as my resisting force. I can watch the column of water collapse in as I force my back into it. If I feel a solid 'thud', I know I did it right.
With a can opener (same except you hold one knee to your body) you can aim that jet at 45 degrees. It creates a little less force but it can be very precise. With just a little practice I can soak someone in a reclining pool chair, 20 ft from the pool edge, while the two chairs adjacent will receive barely a drop. Easy to aim. The jet will emerge in the direction of your head. Just hold your position with your knee held against your chest and the other leg outstretched until you're nearly head-down inverted. When I was a kid, two of us would simultaneously hit the lifeguard and get booted for a week. There wasn't a dry square inch on his body.
I'm in Canada now, but as a boy learnt this important life skill at Booragoon public pool in Perth WA. Then we called it the jack knife. I have fine tuned it the last 50 years and feel "the mummy" is a better name. Arms crossed and hands on opposite shoulders and arms tight to body. Legs slightly bent and body leaning back a little. There is a feel when you do it right. The explosion is just above your head. Everyone looks.
A Grand Manu is a most excellent way to draw attention away from the cool kid who just did the perfect swan dive.
I learned a variant 45 years ago when watching friends. I Worked at a municipal pool. The technique was slightly different - one leg was held with the hands and I don’t think there is time to actually lean back while you’re hitting the water. When the unheld foot hit the water it was at an angle and that would torque the body around.
It's amazing how much you can capture with that slow mo camera. It doesn't look like anything without it but MAN does it look cool when slowed down!
Go back to the mid-late 70s I was doing "Preacher Seats" where you hit feet first and lay back covering your face to take less damage from the returning water. A trick hard to simulate mechanically is making yourself smaller on impact and nearly doubling your volume immediately to suck a lot more air in causing the resulting boom to sound a bit like a quarter stick of dynomite. Same trick for a "cannonball" to double the splash. Did it off the 30 ft platform once and exploded my shorts, bloodied my nose, and knocked the wind out of me. The 50ft was MUCH worse and the life guard had to come get me. I was maybe a buck twenty then!
you have to hook with your feet after penetrating the water's surface to force a faster rotation, also, adding rotational energy before hitting the water is ideal, usually starting with your head and shoulders forward as you initially jump
When i was a Kid i seen this olympic diver doing a double back manu off a handstand at our town pools..His form was tremedously perfect
You can make them with your hand too. If you slap your hand down the right way (like an upside down cup) at the right speed you can send a shot of water very high up (or even sideways (at a bit of an angle) and can hit people about 6-10 feet away (with the water splash that shoots out).
This was a huge thing amongst kids back in the 70s wherever there was something to jump into water ,trees,bridges anything
When we were kids we spent a LOT of time doing this. You straighten out after you hit & go under the water to get the biggest splash. We used to call it 'lay-backs' in Australia.
I used to swim and dive competitively back in the seventies and I could do what they call a can opener and it would shoot the water straight up just like you described I never know how it worked though thanks for clearing that up looking forward to your next video catch you on the flip side my brother. ✌️
In olympics, Divers try to minimize this splash as it counts to the score. They bend their body in such a way that area of surface that comes in contact with water would be very less and hence less splash
ok so I got an idea. Try to catch the water jet the metal ball made. I wanna see if the ball shoots more or less water equal to its weight.
I used to do manu bombs at the Te Rapa pools in Hamilton as a kid
I had never heard of this, but I'd do something similar to get really big splashes in the pool with my siblings. I'd cup my hands to get an air pocket, and push them down into the water really fast to force the air down, so the water would fill it and splash up really high
This is also how torpedoes work. Their explosive charge doesn't do the damage itself, it creates an air cavity and the water jet punches through the armor
So... what we see with the 'manu ball' is they are using the water to transfer a lot of the energy from the diver to the soccer ball. Diver jumps in, punching a hole in the water with his kinetic energy. Water momentarily stores this energy as a 'hole' and the ball 'falls into the hole'. Then when the water collapses around the hole, it thrusts the ball upward with considerable energy. A neat display.
In Aus we kind of do the opposite - where I'm from we called it a horsie; instead of landing on back you land kind of all fours and straighten out as, or just before your torso hit water. This also seems to make big splash.
in USA we have always called that move "the butt buster"
When I was young, we did "Can Openers". I'm old AF, and sure that technology has improved dramatically since.
Can confirm. I remember doing this as a kid ... And adult. There's a variation of it where you run as fast as possible, that creates a very forceful wave.
2:51 should be "so almost the entire volume of the cavity collapses in on itself." You can still see the bottom portion of the cavity bubble that doesn't joint the rest
I was just searching action lab videos hoping he already made a vid on it and sure enough he did! Man has vids for everything!!! So grateful 👍🏼
I called it the jack knife back in the early 1980s. Jump out straight as a board with your feet into the pool and your head closer to the pool wall. Extend 1 leg, bend the other knee and grab it. You want to land with your feet barely hitting the water first.
I did this off a 9' high drive. The concussion nearly knocked the wind out of me but people were in shock at the result. The high dive was soaked underneath.
best way to make a big splash or rather a high or long splash (and I've never heard of manu) is to hold one leg up to your chest with both hands or arms really with your knee bent of course; keep the other leg straight and pointing at the water. You can let yourself lean back a little as you hit to control the direction of the waterjet, so whatever you want to hit, you would be facing directly away from while you lean back. I've hit people a good 30 feet away from the pool. Don't do it off of anything really high as the collapsing water can break your neck.
You're leaving out what I consider the most curious part of this experiment. You have shown a very close example of it despite the crude set up but when done under certain parameters the potential energy reaction creates a helix 🧬. I think you should do a post with a hypothesis on why this occurred
Totally just made me think about black holes watching the way the water interacted to the ball. The cavity is made by slowing the mass. The roles around out that you could imagine as gravity waves, the way the water started to rebound around the circular hole made in the water which would make it hard to see what was happening down in the hole and then just like a black hole it creates the jet straight back out of it. Needless to say this is only an analog and didn't represent the actual working of a black hole but it sure is fun to let the mind wonder.