Breaking Pole Paradox- center of mass // Homemade Science with Bruce Yeany

The Breaking pole paradox is not really a paradox but I didn't name it. This demonstration starts with a long thin wooden pole supported at either end atop two water glasses. A swift impulsive blow breaks the pole at it's center without managing to knock over the cups and spill a single drop. How is it possible? I am breaking it against the inertia of the pole, Swinging the metal bar as fast as I can with a quick hit would cause a quick downward acceleration on the wooden pole. But, since the wooden pole has a certain amount of inertia, it can't withstand the sudden acceleration force and so instead of being moved downward it simply breaks. As the pole breaks, the downward force is now acting as a torque, which now causes the two smaller pieces to rotate around their new respective centers of gravity of mass, turning them away from the cups of water and so they remain upright.. If I were to push down on the stick slowly, there would be enough time to allow for the force to be "felt" on the cups and would surely cause them to fall over. The explanation lies in that the force applied to the pole causes the two new pieces to rotate away from the supporting cups keeping them intact.

[@Mysteryskatin]

This guy was a samurai in a past life. That swing is deadly.

[@YeanyScience]

LOL, there was a lot of satisfaction in making this video.

[@Gribbo9999]

And for the next science lesson . "Eye surgery for amateurs using only a metal bar."

[@schadenfreudebuddha]

lucky he didn't give himself a splinter-filled vasectomy.

[@JoshTorresDJ]

schadenfreudebuddha 😂😂😂

[@tupera1]

He's more worried about protecting the floor than his eyes!!! He's pure genius...he wears safety glasses for the out takes, but not for the final shot! Stay far far away from this one children!

[@saintpine]

If you know physics, the wood could not come backwards high enough to hit his eyes.

[@myhn7227]

Your videos make me feel more passion for physics🙌🏻

[@YeanyScience]

thank you, it makes me feel it was worth the effort when I get comments like yours

[@IvanIvanov-dobry]

@@YeanyScience passion for errors and problems in physics` knowledge)

[@TheLordHighNoob]

AAAAHHH! Coca-Cola! The American Water!

[@noahiscool9002]

Stefan Massyn i was looking for this comment :p

[@AstroEngiSci]

By far the weakest Coca-Cola I've ever seen, though.

[@8bit_pineapple]

Naa, that is LA tap water.

[@Chris-fu8ov]

dyed water in a cocacola container so it'd be easier to notice it spilling

[@sancho5290]

The Limpest Blitz Kit- thanks for posting that you fucking genius

[@scottishfella2680]

that is some dank water

[@FictualKyle]

Scottish fella I will knock you the fuck out m8

[@im.empimp]

I guess he's in Flint, MI

[@xbreathingisirrelevantx]

+emp imp solid reference

[@patrickkeller2193]

At first glance I thought it actually was coke.

[@Bikewithlove]

I especially liked the blooper which shows that it actually did work perfectly, and it was the uniformity of the break that caused the pieces to collide. Before the slow motion part, I thought it was because the wood was struck off-center. That was cool!

[@greg55666]

Dude, where are your fucking goggles!?!?!?!?!

[@Grumpher]

Don't forget your safety squints kids

[@greg55666]

+ImGrumpher hahaha! That made me laugh.

[@Grumpher]

You can thank youtuber AvE for that!

[@remainingrex9471]

ImGrumpher Safety squints

[@saintpine]

If you know physics, the wood could not come backwards high enough to hit his eyes.

[@noahm4601]

does anyone else stop the video to make a prediction of what's going to happen and why it is going to happen?

[@madscientistshusta]

Patrick Ross lol

[@madscientistshusta]

Patrick Ross I invented this new thingy where u like think a thing then guess a thing based on that thing, then you watch the thing and see if that thing happens and things, I call it "the super nerds science-y- method of sorts!"

[@madscientistshusta]

(and things)

[@joemieszczur9735]

lol that "water" tho. is this school in Flint, MI?

[@anita.b]

Gotta love non-corporate water in the US in general.

[@JohnDoe-rq9hr]

Anita K b-e-a-utiful you are. :)

[@RobRobertson1000]

I wish I had had a teacher like you in science class :)

[@Neumonics429]

I love the slow-mo after where he checks to make sure the glasses really didn't spill.

[@MagnusSkiptonLLC]

Cool! I once had a crazy awesome physics teacher that did stuff like this too. Once he tried to demonstrate centripetal force using the typical water in a bucket. The problem was, the string he attached to the bucket wasn't strong enough so on the first swing it broke and that bucket went FLYING. Fortunately, he did it in a plane parallel to the front row so it didn't hit anyone.

[@RobertKreegier]

Don't forget your safety squints, kids

[@CNSninja]

Robert Kreegier You mean 'don't forget your safety glasses, squints.'

[@metleon]

The fail is the most beautiful part of the video. The two boards are just barely able to hit the boxes.

[@MrDaraghkinch]

Looks very cathartic! So much fun you had to do it thrice. ;) Great job, I'm sure your students love you.

[@IferMasterofFire]

"water"

[@xonxt]

More like "wooter". I dunno why was he saying it like that.

[@IVIusicFiend]

xonxt the same reason Brits say bot 'ole when pronouncing bottle. It's called an accent, in this case a Pennsylvanian accent.

[@zarblitz]

Because he's probably from Pennsylvania or Maryland.

[@randeepkang8780]

Ivo van der Hoeven "wooder"

[@SuperMagnetizer]

wudder

[@DireBadger]

Bruce you are awesome. I cannot stop watching your videos.

[@robertzeurunkl8401]

I'm going for an explanation that involves inertia. ;-) It's the same thing when shooting a bullet through a telephone book. You could setup a telephone book, on end, and try to push a screwdriver through it. All you will do is push the book over. But if you shoot the book with a rifle, (I do not know how to explain it technically), but the faster the bullet tries to accelerate the book, the more the books inertia pushes back. It wants to stay where it is. So the more... no, the faster the bullet tries to accelerate the book, the more it's inertia wants to keep it in place, allowing the bullet to actually bore through it. Same thing with this stick. Now let's go watch the video and see if I'm right. ;-)

[@robertzeurunkl8401]

Well, he id mention "inertia" just once, very quickly. He seems to be explaining why the board jumps up OFF the cups (because the spinning around center of mass). But he's not explaining how he can break the board itself without pushing the glasses down and over. But a fun vid. Will def check out some of his others.

[@shadowpig60]

Basically, except its a different idea just because its the breaking of the board on impact vs letting the board flex and snapping. If he hit slower and weaker and let the board flex at all it would tip both glasses. He is basically cutting the board, and since its blunt the board still holds the inertia, but its already broke in half so they don't have direct downward force instead they act like if you were to hang a pencil of the desk and hit your hand on the hanging part.

[@napalaprentice]

the camera looks tilted and its driving me nuts.

[@MO.MOUNIZ]

Thyrne I can't unsee that, thanks to you.

[@christnt9656]

4 minute dutch angle

[@madscientistshusta]

Thyrne it is.

[@pokeygalaxy]

AH...yes..very nice.. every time I see your videos pop up on my feed I click it because I usually learn something new each time. Thank you sir!

[@xMrJanuaryx]

World please meat Bruce Yeany. Bruce Campbell's evil twin brother. Don't let his shy demeanor and inquisitive mind fool you. He may not have a chainsaw for an arm but did you see how hard he swung that metal rod?

[@SarSaraneth]

Not very. His movements were slow and weaker than they could have been. It was a very poor swing.

[@Leeeeem5v2]

Awesome Teacher, Wish I had this in school. A Teacher with passion as well as personality.

[@johnfraser8158]

I would have liked to see what happened if you pushed on the wooden bar to knock over the glasses.

[@mociczyczki]

small force water pour out .

[@deaconblooze1]

That 'mishap' was a one in a million shot. Cool that you got it on camera.

[@dananajj]

What happens when you hit it too gentle? Btw, I love your approach: you give an awesome demonstration and leave the full science unanswered so that kids can go away and find out for themselves.

[@johnmilner3030]

love the combination of the pink towel with the kelly green one. very preppy.

[@hardrocklobsterroll395]

great video as usual Mr yeany

[@etrou4]

That's amazing. When everything goes well, the only thing that makes the water glass move a little bit is the vibration from the shock that gets to the glass before it starts rotating.

[@gregcollins3404]

the trick is to break the stick fast enough so that the net acceleration of the ends is upward. The impact on the stick accelerates it downward, but when broken the ends accelerate upwards.

[@borischan5252]

So why is this a Paradox?

[@shadowpig60]

My only guess is that he was taught this trick a while back and who ever taught him gave it this name, and he hasn't came up with a more fitting name.

[@borischan5252]

***** Yea well, it is just that something so obvious, or at least so easy to understand for ppl who haven't studied science, is unworthy of the term

[@seancoyote]

Because the simple assumption is contrary to the outcome. For instance, standing still is more tiring than walking. The assumption is that not moving is less tiring, but in actual application, less muscles are under more strain standing still than many muscles walking does. With more information, the problem isn't a paradox. With the paradox shown in the vid, the simple introduction and assumption that the same physics apply with applying pressure to the center should result in similar outcomes, causes the outcome to be paradoxical. You see, this show isn't really for people knowledgeable in all science, and to a simple understanding, this is paradoxical.

[@ibrahimturan28]

When science gone mad. in this video he is bruce lee. Keep uploading new videos, I LOVE IT.

[@shrine010]

teachers like you are the best :) it's all about passion

[@c42cly]

I love it! Great demonstration. I wish I had you as a teacher...... The best

[@DANGJOS]

Interesting thanks. But you need to learn what an actual high speed camera is lol

[@YeanyScience]

LOL, I tried but it is a piece of junk, the picture was so grainy I couldn't use it, if I had, I'd never hear the end of it.

[@DANGJOS]

Bruce Yeany Really?? I thought those things were expensive. How could it be bad quality?

[@YeanyScience]

It is a cheap Casio point and shoot camera

[@DANGJOS]

Bruce Yeany Ah so not high speed at all

[@SilverJigProductions]

Most smart phones these days can shoot pretty decent high speed! Or if you could get your hands on a GoPro. 120 frames would be good enough for this stuff. :)

[@Gkuljian]

OK, that was good. I predicted a silly demonstration. Excellent. Now you've got me thinking again.

[@kirkjohnson9353]

The most surprising part was that he called that stuff water . (just joking around. Nice video)

[@notsorted8368]

You make great videos, thank You -an Armenian guy with bachelor of physics from Armenia

[@YeanyScience]

Thank you, nice to hear from someone in Amenia

[@thevileirish6764]

your frikin awesome Mr. Yeany love your videos on physics

[@YeanyScience]

wow, thanks, I just enjoy what I do

[@highanddryful]

LOL it’s 4am and I’m not asleep or maybe it’s a dream... Love this channel

[@BryonLape]

There is no board.

[@Matt_Lifts]

Bryon Lape my whole life is a lie

[@jth_printed_designs]

It is not the board that breaks, it is only yourself.

[@bobbypatton4903]

And he'll use the metal rod on your head if you don't pay attention in class!

[@TheEbola1994]

More teachers should be like you, then the attitude towards school of many students would change

[@ewauvwas]

Your Channel is GOLDEN

[@YeanyScience]

Hey thanks

[@OG_Zlog]

What happened to the Highspeed?

[@YeanyScience]

It is a cheap camera and the video was too grainy to use, I need better equipment

[@OG_Zlog]

Oh okay, I just saw you set it up and then it didn't show up in the video. Great video by the way. Very interesting.

[@edwardholmes91]

Great demonstration Bruce, got to love the outtake too :)

[@chasebh89]

I love watching Bruce Laurel's science videos

[@ColdieHU]

lol this is what happens when science teachers stay in school after everybody else is gone.

[@rogeronslow1498]

This reminds me of the falling chimney problem. The falling brick chimney (or smoke stack) almost always breaks about two thirds of the way up before hitting the ground. The reason is that the chimneys centre of mass (located around the center of the structure) is accelerating at g while the top is accelerating at greater than g. This higher acceleration causes a bending moment along the structure which it cannot support and it breaks before hitting the ground.

[@jimfindley1004]

i find the fact that both glasses fell down at the exact same time and direction on the failed attempt amazing in itself

[@NickRoman]

so, the fail at the end was because he did too good of a job

[@buddmac4315]

Nice! I appreciate the explanation of the seemingly fail at the end. thanks

[@TomLeedsTheAtheist]

Love it Bruce! And I really like finding these simple experiments that I can do for my 8 year old and her friends to both entertain and educate. And I'm glad you included the one that didn't quite work out, even when it goes right it can still go wrong.

[@dougshade2]

Awesome... please continue to encourage kids to experiment... but safely. Wear your safety glasses ALWAYS. Cheers!

[@YeanyScience]

thanks, missing glasses, my mistake

[@WilliamCrump-Celestia]

FUCK SAFETY

[@Art-ej6xk]

His slow motion face when he's whacking wood is the same face he makes when he's whacking wood at home.

[@japeking1]

Thanks for the stuff up bit.... I almost always got more stuff ups than successes . Kids seemed to enjoy it just as much.

[@domcap70]

Someone buy this man a high speed camera

[@ChipMaker1066]

And some safety glasses.

[@YeanyScience]

sounds good to me, mine is a piece of junk

[@edwardhall2975]

this is what youtube should be all about

[@BeanzyBRO]

What kind of water was that 😂

[@OutOfMemoryException]

Good one.

[@GoldSrc_]

Tell me, would you be able to see how the water behaves if it's clear water?, this is science, you add color to the water to see how it behaves.

[@Radonatos]

The Clickbait Paradox: - You know that the 'paradox' promised in the title is probably just some mundane physics, yet you still click on it. The Science Paradox: - You try to explain science, yet you do not know what a 'paradox' is.

[@YeanyScience]

I do know what a paradox is, however, this demonstration has been around for years, and that is the name that it goes by. I did not name it

[@ivancarrero9405]

this should be awesome if you had a slow motion camera.

[@YeanyScience]

I have a cheap one and the shot came out too grainy to use

[@ivancarrero9405]

Bruce Yeany thanks by answering and i hope you include the slow motion in future videos. LIKE

[@YeanyScience]

I probably didn't have enough light, but yes I will try to use in future videos

[@DeathBringer769]

Yes, high speed needs a lot of light. The slower, the more light you need.

[@ercost60]

Terrific videos all, Bruce. LOVE your channel.

[@Willthebeast2987]

that is not water

[@DevotedPastafarian]

Will The Beast 2987 you've obviously never been to flint

[@yrussq]

Magic! Practical physics is fascinating - but you reeeeealy should buy an ultra hi-speed camera for these things. It's cool, it's stylish, it's informative, it's a must have. Because now i really don't catch the movement of the pole thus don't understand the forces, their vectors and deformation types. Cool channel, Bruce! Best regards from Russia!

[@bledlbledlbledl]

What he's not telling you is that on his first try, he broke one of those overhead fluorescent lights with the metal rod while taking a swing at that board, and shocked the snot out of himself.

[@02BLACKTAWS6]

Did the bong water provide a heavier, more stable base in which to conduct this exercise?

[@ninjarooster9258]

This is why, as a martial artist, I can break boards tossed in the air.

[@jojothermidor]

Why couldn't my science teacher be like this v_v I'd have loved learning.

[@systempatcher]

I see, the board is broken before the vibrations can each the cup. By then, the board is in two pieces and the rest of the kinetic energy causes a spin on the pieces.

[@talexander7217]

Judging by the color of the water and lack of students, I would say this school is in Flint, MI.

[@carultch]

He added food coloring to it. The school is actually in Pennsylvania.

[@ModernProspector]

"Breaking Board" in a science classroom ......lmao. Is this the real Walter White

[@noealva]

So if you wouldn't have broken the board the cups would have tipped over, right?

[@shadowpig60]

If he didn't break the board it'd tip. But even with breaking the board if it was broken slower it still would have tipped. The trick is the him slamming the pole into the board its breaking on impact, not snapping in half due to bending.

[@DeFransWorld]

this guy is a wizard

[@josefpm]

Amazing!, and the final behind scenes fantastic. ( ¡Alucinante! y el detrás de las cameras al final fantastic.) Thanks, gracias.

[@YTGhostCensorshipCanSuckMe]

put the cups at the fractional distance 0.25 and 0.75 along the beam an see what happens

[@mynameiseilers]

please be my new physics teacher.

[@mattmn23]

So what would happen if you had a piece that was longer (Twice as long I suspect?) to where when it was broken in half the new center of gravity for each piece was over each glass? Could we then expect the broken pieces to tip the cups over?

[@YuvalBelisha]

Thank you for the mental challenges!

[@The177Hunter]

*_WHY WERENT YOU MY SCIENCE TEACHER IN HIGHSCHOOL_* also, expression at 4:08 was priceless

[@wardified8566]

You're A wizard Brucey!

[@harrychristenson4938]

yeany is a beast. he knows how to get down

[@Observ45er]

Hi Bruce. This is a really slick demo that I hadn't seen before. I just use a block sliding on a dowel and tap on the dowel, but this one really spices things up!. ... A couple of points. ... In the vid it is a "board" and in the descript it is a "pole". ... *_THE_* key concept here is that when a force is not directed through an objects center of mass, a rotation, or torque, is imparted. ... From some confusion in the comments, perhaps some editing may help. I think this sentence may be misleading because the center of the long pole *_DOES_* move downward due to the 'hit'.: "But, since the wooden pole has a certain amount of inertia, it can't withstand the sudden acceleration force and so instead of being moved downward it simply breaks." ,,, It might be clarified something like this: "But, since the wooden pole has a certain amount of inertia along its entire length and it is not completely rigid, the center of mass of each half is not accelerated downward, but "tries' to stay in place. Since the center of mass of the half-pole does not have a force applied directly to it, it will stay in place due to its inertia. The fast motion at the hit-point now is working against the center of mass of the half-pole so the half-pole starts rotating around its center of mass. ...I'll be breaking poles soon...! -- Regards, ScienceAdvisorSteve challengerillinois.org

[@YeanyScience]

HI Observ45er, nice to hear from you again, I appreciate your comments on this and will try to clarify it a bit. I've taken quite a few comments on this and it is such a good demonstration I'm thinking of redoing it and try improve the quality. It was also one of the most fun to make. However, between school and other activities, and other videos in progress it will take some time to get to it. Thanks again

[@djdradp8baller2]

Safety Glasses? ahh Im over here squinting my eyes for him!

[@TheNumberScott]

What happened to the clip with the high speed camera? And why does the board break without applying pressure to the cups first? I get that the center of mass changes after it's broken, but shouldn't there be pressure as it's breaking?

[@YeanyScience]

Sorry, but I have cheap equipment, the high speed camera video takes was pretty much worthless so I took the regular shot and slowed it down. When the stick is hit quickly, the downward force or torque causes it to spin away from the cup

[@Diamonddrake]

The actual trick here is inertia. The board has mass, and so it resists being accelerated. Since the metal bar has much more momentum, it imparts a great pressure that causes the board to break, then once its broken, all the kinetic energy is on the ends of the new shorter boards, so they introduce a torque, that causes them to spin away from the glasses. Basically if he tossed the wooden bar into the air, he could have struck it downward while it was in the air and it would have behaved identically. it doesn't need anything to hold it, thanks to inertia, no extra normal force is needed to break the wood. As long as he strikes it with sufficient pressure, it would break even if it wasn't being held at all, or if it was floating in zero gravity.

[@TheNumberScott]

Thanks Diamonddrake, that's a pretty good explanation. It would be a great video too to illustrate that that is what is going on, if someone were to make it.

[@Bloodsong13T]

hey, great demonstration! and a blooper too (with science!) :)

[@infinity.1111]

I feel like this is common sense with arrows and terminology added to it. You have a killer swing though and I like most of your videos.

[@carmelpule6954]

The explanation this gentleman gives is correct in every manner, but may I look at it another way. Obviously the source of energy that is involved , it all starts with that rod in his hand swing down fast or slow where the nature of that energy will cause a WAVEFRONT to proceed along the horizontal rod. The nature of the distribution of weight along the horizontal rod will decide the manner in which the wavefront travels along the horizontal rod, and it may be regarded as a transmission line where the wavefront speed depends upon the characteristic "weight" per unit length of the horizontal rod. In every tranmission line there is a delay as the wavefront travels along it to reach the other side. *I am going to suggest that the nature of the speed at which the vertical rod touches the horizontal rod, it could be compared to a DC or an AC voltage applied to the end of a transmission line. If the vertical rod comes down very slow compared to the speed of the wavefront along the horizontal rod, the inertia at the centre of mass on either side is not effective and the force will arrive at the support points the whole lot acting as a normal beam or lintel. * If the downward force is fast then dynamics will come into it and the whole force will be impulsive and the energy will be basically stationary acting on the centre and most of the energy will go to break the horizontal rod, but to break the horizinatal road the centre must move downwards, and the wavefront is slow and the broken half of the horizontal rod will not have the wavefront along it reaching the position of its centre of mass and so the action is now of a large moment on the centre with the picot point at the centre of mass which due to lever system the pivot points will rise and not fall. It is a brilliant experiment with lots of scientific components coming in. Congratulations for this demonstration and now for the differential equation describing it. I consider all this as art and science combined and it is not appreciated by may artists not theoretical academics I am afraid. I was a little compassionate towards Mr Bruce Yeany when it did not work as he was stunned by the results as he was completely confident of his work but the different states that occur in that experiment occur so fast that the poor man did not realise that the experiment did in fact work and it was only the halves of the broken rod that hit the support car board boxes that caused the downfall of the glasses and it was not the experiment failure. Many teachers do not show demonstrations like this because they involve time, and the carrying of equipment and most educators all they like to carry with them is their own weight. Congratulations, Mr Yeany for your good work Keep it up and since it is late December 2016 may I wish you a Happy and a Healthy new year 2017

[@carmelpule6954]

On thinking about this problem, I would say that if the vertical rod is coming down very very fast compared to the elemental weight per unit length of the horizontal rod, the break at the centre is due to shear force as when the vertical rod touches the horizontal rod , the side elemental inertia at the the point of contact will be too heavy and shear will take place rather. Obviously this is taking the issue to the limit, but it shows a deeper understanding of the real issues taking place. It is all beautiful invisible art to the human eye as the eye have only a " slow" capturing speed capacity........... or should I say the transmission of the wavefront through the optical nerve to the brain which has too much delay and the algorithm in the mind to work it all out is also a little slow with its own thinking inertia. Would love to see the mathematics which describe all this. But not on Matlab as the video shown is better than graphical solutions on a computer screen.

[@moywalch44]

I really liked this video because you took some time to explain a principle (even adding the image or something) All your videos are amazing, but as a person who is seeking more knowledge; sometimes I'd like to know a bit more about the scientific/physics principle

[@7F0X7]

This reminds me of my high school physics teacher except he was usually trying to hit us with things...

[@tuckertoden]

This may be a stupid question, but if the center of mass "moves" from the center of the board to halfway through each of its two new pieces, could the movement of that center be said to be going faster than the speed of light? I understand it isn't an actual physical object that's moving. Just a weird thought.

[@Observ45er]

+Tuck Oden It doesn't "move". The Center of Mass (CM) depends on the mechanical objects. At the point when the bar hits the center of the board, the board becomes two independant boards. The center of the larger "board" then becomes a joint between two smaller boards. This joint is now a flexible joint (like a hinge) by virtue of the pipe hitting and flexing it there.

[@ChineseSweatShoppe]

As much as I despise patreon I would still support your channel.

[@satisfiction]

Great videos! I do wish you had a real high-speed camera, though. ;)

[@Henry-cb7fg]

satisfiction could have been helpful

[@jaystevens427]

I always loved science in school but unfortunately for me my teacher was a bore! if this is how he teaches his classes, then his students r lucky to have a fun teacher. I'm not even in school anymore but I'd love to go back and take his class. keep the videos coming Bruce! oh and FYI...if that "water came from the schools tap, please for the love of God DO NOT DRINK IT!

[@aerobyrdable]

Good video, Thanks :). You shouldn't show up late to filming, though. You'd think they could have at least waited for you to get in position before starting :D.

[@YeanyScience]

Hi Ryan, thanks, I make these videos when I get the chance so it may be at odd times during the day. I do all this myself so I have to walk back and forth to start and stop the camera

[@flagpoleeip]

what do we think paradox means?

[@peepiepo]

Often things have the word paradox in their name when they simply appear paradoxical even though they technically aren't. For example, the Birthday Paradox

[@flagpoleeip]

Old Uncle Silas good answer.

[@Skunkwurx]

If you actually bothered to read you might have realised he didn't name it....

[@zackeryrice9597]

you forgot safety glasses. "safety is number one priority"

[@SoLowKaspar]

You're a wizard Harry

[@lheofacker]

The principle behind this whole thing is already clever, but the reason the water spilled in the end is way clever-er!

[@billtruttschel]

It was weird, in the blooper at the end of the video, the glasses seem to fall in a similar direction as opposed to a mirrored fall.

[@imduncanmajunkin]

To be honest, I was really hoping you would have taken out a light fixture on the first swing. But interesting video, middle school kids would love this

[@dananajj]

3:00 I thought after breakage, the pivots would be at end points. I think the diagram should have reaction forces pointing upwards acting from the cups to better explain why the two pieces of wood now rotate about the centre of masses as indicated in the video.