Steve Mould - 2022-02-18
Offset your carbon footprint with me using Wren. We'll plant 10 extra trees for the first 100 people who sign up: https://wren.co/start/stevemould Parametric Resonance is when one parameter of an oscillator is varied at the right frequency to cause the amplitude to increase. Autoparametric Resonance is when that happens automatically! Here's my video on resonance: https://youtu.be/dihQuwrf9yQ Here's my video about an upside down pendulum: https://youtu.be/gnn21smGVrQ Here's my video about a levitating liquid pendulum: https://youtu.be/gMAKamGIiMc You can buy my books here: https://stevemould.com/books You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Alan Wilderland Joel Van der loo Glenn Watson Doug Peterson Paul Warelis John Zelinka Alnitak Grant Hay Heather Liu Marshall Fitzpatrik Lukas Biewalk JJ Masson Ben McIntosh Damien Szerszinski Matthew Cocke Frederic Merizen Jeremy Cole Frank Hereford Will Ackerly Brendan Williams Cameron Leigh Middleton Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk
I design ships and they can actually experience a form of parametric resonance called parametric roll. The ship’s stability is a function of its waterplane area. Waves can affect this, by changing how much of the ship is in the water at the ends. You can think of this as a torsional spring, with a variable spring constant. If the wave encounter frequency is at or near the ship’s roll frequency, the ship will begin to roll very violently, even in relatively small seas. This effect often causes container ships to lose containers over the side. They deal with this by slowing the ship down, which changes the frequency the ship encounters the waves at.
That is amazing and scary. Amazing that it's such a universal concept.
one step forward two steps back 🚢
That's a fascinating example. Thank you!
How long does it take for you to design a ship?
Thats pretty smirt stuff i actually saw a video the other day of bill nye explaining this on noahs arc and the worlds largest wooden ship it would probably be a really cool short video to check out since thats ur profession
"The size of spring was starting to get into dangerous territory, like garage door spring"
As a garage door tech I appreciate that comment. Working on your own door is statically as dangerous as working on your roof. I've known plenty of other techs and home owner with ER trips and a few that passed from being careless.
A kid in my high school was doing something with his Jeep and failed at the DIY spring compression device. He came in to school the next day with a hole in his cheek! People are way too comfortable around springs and tight cables, ropes and stuff.
You could probably do an autoparamatric resonance with a swing by both translational and rotational modes (instead of using a big spring). I'm sure I'm not the only one who as a kid remembers finding that one cheap swing with the rope attachments too close together that no matter how hard you tried whenever you tried to swing on it it you would just end up spinning eventually instead - likely autoparametric resonance between those modes.
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@MaxUgly considering that the whole weight of a car is supported solely by 4 springs, and remembering that those can withstand potholes and speedbumps without issue, shuld be enough to scare people into handling with caution.
You cant compress a bike spring with your full weight, let alone a car spring!
@TheNasaDude Well, go back in time and tell that to my classmate in 2004! sheese man you act like I told him this was a good idea.. unbelievable, I'm gonna go chew on a ball bearing now..
Steve's dedication is just amazing! He's spent years to raise his latest physics teaching prop.
lol
As a fisherman I know this phenomena all to well (parametric resonance). Any time I throw my bait over a branch or something I use this method to swing it free.
With my skill I usually tug a bit too hard and end up hooking the branch like a grappling hook lmao
@100GTAGUY yup I have this luck then I switched to spiderwire 80lb and now I either straighten my hook or get a free branch lol
@Wesleystewart78 on the upside you can skewer your fish with the branch lol.
I usually end up going after my lures and hooks and hand retrieving them off the branch, and or taking a swim.
Oh wait... You're right!
also very evident in the flyfishing casting techniques
6:38 I discovered this as a child and was able to get to get as high as the bar of any swing with almost no effort in as little time as possible. Imagine the heart attacks my parents got each time they'd arrive at the park and see their 10yo (with Moderate Haemophilia) standing on a 3m-high swing going higher than the bar.
The issue with your form from what I can tell is that your legs are still bent while you're travelling upward, so you're unintentionally pumping into the swing. Whenever I stand on a swing, I'll only slightly bend my legs and make sure my legs are fully straightened at the same moment I reached the bottom of the arc. I'm not sure if this is accurate scientifically (but it makes sense theoretically) but I found that it was the easiest way to go super high super quickly
That sounds incredibly terrifying, God bless your parents
I'm doing this the next time I find a swing
We had a wooden swing set behind our house which featured a two-person "horse", which was a plank for a seat connected by two hinged joints at either end to two other planks, each of which had foot pegs and handlebars. The swing was suspended by a pair of ropes which ran between the handles and the frame. By standing on this in a surfing posture, you could get really high very quickly by leaning away from the direction of travel while pulling on one set of ropes while pushing on the other--essentially what you described. The ropes weren't nearly long enough to swing the full 180 degrees, though.
I've seen acrobats do the same thing :)
It’s amazing how many things get discovered by pure chance from the exact right combination of things.
Like cutting a grape in half (but leaving it connected by a little bit of skin)and microwaving it, turns out it refracts st exactly the length of the wave of a microwave and starts to glow white hot.
Which sane person microwaved grapes after failing to cut it in half
@Brian Evans which is why insane people make discoveries lmao
"You're just shoving the thing, repeatedly."
-Steve Mould, describing the gentle act of pushing a child on a swing, 2022
accidenaly breaking the childs back
shortly before giving the child whiplash to make a scientific point
Physics doesn't care about the child, any object of the same mass would have sufficed.
gentle act? that child's spine was shattered in the end.
In my brain, this moment is filed away right next to Dennis Kucinich holding a baby doll by its neck when challenged to problem solve by David Letterman.
I used to have this bungie rope swing when I was little. I always used to wonder why It would bounce around all weird when I tried to swing normally.
I guess this is why!
Honestly I think Steve Moulde is one of the few good science teachers
I feel like a lot of science teachers are passionate but end up being basically glorified magicians
Showing us that something can be done without really explaining the how of it
I remember learning this in my advanced mechanics class. I had never seen the spinning/twisting mass on a spring one though. That was super cool to see.
I was vaguely aware of the non-auto variant, very interesting concept. Also a fascinating demonstration seeing it shift multiple times between primarily working as a pendulum and spring... converting the energy that's in the system between the two states. At first it really seems like something that should not be happening.
I'm glad Steve mentioned the double pendulum that is loosely coupled. I run into a similar thing carrying my water bottle (it has a string tied to the top, making it a mass at a short distance) and lunch kit (a larger mass at a longer length). I wind up swinging my arm slightly, causing both the water bottle and lunch kit to oscillate rhythmically like a loosely coupled pendulum. Turns out the masses and lengths are such that my water bottle moves counter to my lunch kit and I can feel the resonance build up if I don't slow my arm down.
This is actually how continuous Foucault pendulum demonstrations are typically powered in museums, since you need to keep inputting power to keep the oscillation going without pulling the bob in any particular direction or influencing the rotation of its plane of oscillation.
Oh cool!
O cool!
Owe cool!
I had wondered about that, but never bothered to look into it. Neat!
Hey, Steve! When I was 6 or 7, my grandfather in west Virginia built my cousin and myself a swing set... I noticed over time that pulling backwards (perpendicular to the chains) as hard as I could while I swung forward, then releasing as I went backwards, that it greatly contributed to how high I would swing. I still pumped my legs, but felt as though this almost doubled the efficiency I could gain height at...Being a child at the time, I obviously didnt understand it from a physics standpoint, but is THAT not an example of parametric resonance in swinging? Just curious, thanks a lot!
I freaking love this channel! Steve you are such a talented and goofy guy, as an artist and audio engineer I really love these especially!
I have a toy kinetic double pendulum on my desk. Its powered by AAA batteries to continue motion, but the changes of phase reminded me of the spring pendulum. I love how you use other examples to get a different perspective!
I wonder if it's possible to get an unstable oscillation that tranfers between more than two modes. 🤔 Like the twisting pandulum goes up and down, can it also go left and right at the same time ? Or maybe adding a length oscillation to the twins pandulums ?
That would be nice to see i guess ^^
I love anything to do with harmonic resonators and resonant motion or resonance in general. I'm a hobbyist electrical engineer, and one of my favourite areas of EE is in oscillators, like ones made of an inductor and capacitor, which work based on a lot of concepts of resonance that can be applied to a system like this. Except instead of the harmonic motion being mechanical, it's electrical. But despite this difference you can use the exact same formulas to describe them. Which I absolutely LOVE it when I find overlaps between two topics in science/physics that seem to be unrelated at first, but when you look closer, you find the reality is that they can be described the the exact same set of rules. It's almost as if the physics is coming full circle or something.
Eh, here I thought we are going to have a new Mould Effect, but instead it already has a boring name as Autoparametric Resonance
It saves us all a month of argument though.
Hey Mehdi!'
Love your videos
Any idea on the next topic?
What about a rotational oscillation that switches to an up and down oscillation that switches to a pendulum oscillation? Do you think this works?
Why did i read this in his voice ???🧐😯
youDisinform.
The Mathieu equation, (pronounced matew or mathew) is a fun equation. There are papers written that describe what happens when tweak various parameters. Parametric excitation is a fascinating topic.
If you perform a multiple scales expansion (I would guess a first order would be sufficient) on your model you will be able to see the slow change from swinging to bobbing in your spring pendulum.
Now what I really want to see is a double or triple spring pendulum, that'd be wild
I would still love to see a full scale representation of this model. Bungee cord may offer the same effect. Interested to see how a pendulum started in parametric mode (normal swing by transitioning angular momentum) will transfer to autoparametric in full scale.
Thank you so much for your videos! You make physics fascinating in a way my high school physics teacher never could.
Another cool thing about pendulums: I saw one where stiffness of the spring was probably a bit different in two perpendicular directions, and what was observed its end made a Lissajou curve.
Swings on springs would indeed be autoparamedic.
Bruh. Report that bot, they are popping up everywhere recently. I’m sure that by clicking the link you get your account stolen.
@Mixer 001 it's upto the creator to run the thioJoe script us viewers can't do anything since the bots will exist even after reporting
@YLava eventually, youtube will ban them.
@MrNerd314 I've been thinking that for over a year now. I think Google gave up the fight.
I recall feeling the breath of fresh air when the 'period of a simple pendulum' formula was recently made precise and concise using the Gauss AGM function.
When I was a kid, pumping a swing was one of my absolute favourite things. It's such an exhilarating feeling!
I was playing with one of those wire note holders/place card holders that's basically a coil of wire for the base leading to another spiral of wire which holds the note. When held at the bottom at certain points and tweaked, it springs back and forth in a very fast blur in one direction and then reverts to a side to side blur. This happens a few times before the dual cycling stops. It doesn't matter if you bend it to go sideways or forward and back, either will bring about the double motion effect.
Holy smokes! The spring pendulum in auto parametric mode describes the same pattern as the Lorenz Attractor: repeating patterns within an outwardly chaotic system. Fascinating stuff, Steve!
I suppose you could also make a system with all three of pendulum, spring, and rotation modes. I wonder if you can get an unstable mode that transfers energy cyclically between those.
You could probably use bungee cords instead of springs for a real-life version of this sort of swing
Oh God, I just pictured of a Bungee jump going horribly wrong by bouncing off to one side instead of up and down. Falling to the lowest point and instead of going up... bouncing off sideways into a rockface.
@Tomos Bungee cables are always tuned in terms of length and weight for precisely that reason.
And that's also why you need to make sure you're working with proper professionals.
Cords are still springs and since they have same energy capacity - till take your arm off just as well.
Bungee cords are way less durable, especially when exposed to UV radiation. Placing a metal spring out of reach of the rider would be a better option
He could just go toprope climbing and swing on the climbing rope at the highest wall his local climbing gym has (preferably not that high off the ground). Climbing ropes are dynamic ie. they are springy and the longer the rope, the more pronounced it is.
It might be interesting to plot the attractors in 2D configuration space :)
Hey Steve! Do you know where I could buy all this sets of springs and weights? I'd love to try these experiments at home. Great and super interesting video by the way!
I would love to see someone use some of these properties in a chaotic pendulum and see if it would become even crazier!
The "other" way to pump a swing is the more powerful one, and the one you normally use to swing 360 degrees all the way around
Thanks for telling about that.
Wait, you can get it to go all the way around? I always ended up falling off the swing when I got to about 120°.
Mesmerizing! I would be very curious to know what parameters affect the period length of the change in oscillation and if we can make it arbitrarily long.
This video reminds me that, back in school, we were asked to do an experiment to fin out what parameters affect the period of the pendulum.
I made the (what seemed reasonable at the time) hypothesis that the mass would affect it.
So I set up my experiment, did lots of testing and, of course, had a negative result. Undeterred I kept testing, being very thorough.
I then got told off, maybe I should try something else.
I didn't get good marks for that experiment.
Which I maintain is very unfair. The point of science is not have the answers before you test, but to hypothesis and then try to prove or disprove!
My hypothesis may have been wrong, but my approach was, I believe, entirely correct.
Everyone else in the class tested length. Statistically speaking I think the majority of them must have had prior knowledge of the answer before starting.
When we found out that our hypothesis was wrong and we could explain why we could still get full marks, that's how it should be
In fairness to you, the density and size of the pendulum will have a very small effect in atmosphere, but it would be difficult to measure that effect with grade school equipment. So you weren't entirely wrong, you just didn't have the equipment to show how air resistance and weight will change the resonance.
You are right. Science is supposed to be a relentless and thorough pursuit of the truth leaving no stone unturned until it's discovered. You should have been praised for your determination not docked marks for it.
Definitely unfair. If each student or group of students used a different hypothesis, together you would have discovered which parameters matter and don't matter. If each team did it rigorously then as a class you would have derived the truth.
Honestly, your experiment was more realistic.
@YannickBo When did it change? I finished school in 2000 and the way you describe it should be is exactly the way I aced all of my physics - a good write up that reaches the right conclusion. Lets see if I still remember how to say out a physics experiment all these years later - Hypothesis, Experiment, Results, Conclusion etc.. haa
I'd like to see this explored further in three dimensions. Like what if you have two pendulums (pendulae?) swinging orthogonally? Or what if the pendulum goes in a circle instead, could the radius of that circle be used as a parameter?
very cool! are these transitions between modes related to bifurcations and differential equations?
Have you tried the auto parametric spring in 3D space? Against the wall the movement it's just an 8 shape. Perhaps in 3D space will happen something more interesting. 😄
Very nice idea, thank you!
Yeah, it would be more interesting, but also much more chaotic. The best (coolest) scenario that I could think of is having the unstablility copied along the 3rd dimension, out of phase with the original instability by exactly one half. Or perhaps one stable phase and one unstable phase would be interesting to look at because one is a multiple of the other, IDK.
Haha I love how you answer questions I've asked myself for years as a child! Great work Steve thank you
There's another thing going on here in your string pulling demonstration, when you give the string slack near the end of it's upwards trajectory, you are also allowing it to extend it's parabolic flight path in the direction it is moving horizontally. This will increase the potential energy for the next swing
"If swings had springs" sounds like a relative of "if wishes were fishes"
I've always heard it as "if wishes were horses, beggars would ride".
@Ken Carpenter "If wishes were fishes, we'd all cast nets" comes from Frank Herbert's novel "Dune"
Repent to Jesus Christ
““Even now,” declares the Lord, “return to me with all your heart, with fasting and weeping and mourning.””
Joel 2:12 NIV
h
@Ken Carpenter “if wishes were horses we’d all be eating steak” can’t remember the show, but I feel like it was said by Jayne Cobb 🤔
If if was a fifth we'd all be drunk.
My final project as an ME student was something like this!! My project takes its form by combining the concept of a see saw and a swing with a spring as a connector, never got the chance to perfect it but this was the main idea.
Great video!
Really, great videos! I really like your content!
Question here: Is it possible to have a pendulum with a spring that goes up and down and that twists at the same time? Kinda triple mode?
Great video! You could use bungee cord for the swing. I actually have been in such a bungee thing doing the moves your pendulum did.
Is there a way to combine Wilberforce pendulum (rotation and translation) and the string and spring pendulum (oscillation and vertical translation) to get all the three modes combined. It would be really nice to see how they would behave.
This makes me think of how muscles grow for strength or flexibility and then how tree branches grow how if you sometimes cut a branch from a tree the whole tree will fall later. Thank you as always for the knowledge porn👍
Whenever someone brings up resonance, I immediately think of orbits, and as soon as you said you have to put energy in when it is moving the fastest I thought "just like it being more efficient to burn at periapsis to expand/lower the orbit than any other point". Anyway, amazing video, and now I want to find other more unusual examples of autoparametric resonance :)
Cool!
@Steve Mould
Please make a video about an oscillator with all three modes of operation:
Swinging, twisting and bouncing !
I suspect it will behave chaotically but I might be wrong.
I’ll have to thank Kerbal Space Program for letting me understand your comment
@Oscar Patxot KSP was where I really started to understand orbital mechanics. At this point I've looked into it a bit outside of the game, but that's where I learned a lot (mostly from Matt Lowne at the beginning).
@Cezar Catalin the wilberforce pendulum can be set up like that. But from what I remember the energy ended up being spread among two of the modes and so the pattern didn't look as pretty.
Steve Mould - 2022-02-18
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Dilbot - 2022-02-18
Think we need to handle exportation carbon emissions first but whatever helps
CRYPTOGENIK - 2022-02-18
Love your videos Steve! Bluest eyes on youtube :P
+Cryptogenik
Jan Girke - 2022-02-18
I would start with the carbon offsetting by supporting solar and wind energy with long lasting batteries like LTO cells. 15 - 30k cycles with 100% C1 and only a degradation to 80%. Don't believe me check it. Looking forward to your solar cell installation video^^ , preferably with LTO battery banks.