The Turntable Paradox
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- Опубліковано 27 лис 2022
- Watch THE LÄND web series here: bit.ly/THELAEND_SteveMould
A ball on a spinning turntable won't fly off as you might expect. In fact the ball will have it's own little orbit that is exactly 2/7th the angular speed of the table. Here's why.
Here's my video about logic gates made from DNA: • I played tic-tac-toe a...
Here's a paper with the calculations: m2.askthephysicist.com/Weltner... Note that equations 18 and 19 should have R² terms. That threw me off for longer than I care to admit!
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I can't believe I didn't make a "how the turntables" joke. That's why I love the comments section!
Here's a paper with the calculations: m2.askthephysicist.com/Weltner.pdf Note that equations 18 and 19 should have R² terms. That threw me off for longer than I care to admit!
What happens with shapes of constant width? My guess is it depends on it's moment of inertia, but still would be fun to see.
Spinning balls. Balls on the table.
You could've done so much jokes...
Have a great day sir!
Also, Baller, Balling.
Does this work with non spherical solids, too?
How about a water filled ball?
It's hilarious to say that the car is pointing "tangentially"-- When in fact, no matter what direction you point the car on a round table, it is pointing OUTWARD; lol.
Our family used to have a membership to a children's museum where they had an exhibit similar to this. The spinning disc platter was probably 3-4 feet in diameter stainless steel. They had a variety of different diameter and thicknesses of disks that you could experiment with and balance on the big spinning disc platter. Was probably my favorite exhibit as it required intuitive interaction!!! Super Fun!!! 😁👍🏻
I'm gonna need a 2-dimensional, transparent, liquid filled representation of this.
😂😂😂
It's the only way for me to understand these things.
Could we settle for a venn-diagram instead? So Kamala will understand too?
Sucks for you
We used to use a tank on a rotating table like this with food coloring to simulate solid body rotation in undergrad. So 3d, but transparent and liquid filled, we're almost there!
'discs behave wiredly on turntables'... that sums up my entire experience of the 90's quite nicely
Weirdly
Wiredly
You can get Bluetooth turntables now, so the discs behave cordlessly.
"90s" "turntables" "behave wired-ly"
Hm, am I overthinking this?
You spun them the wrong way
Well well well, how the turntables....
Underrated comment
There’s always that one guy 😂
How indeed 🤔
This is the first time in a long time that I've genuinely felt fascinated by the application of mathematics as hard-and-fast rules for how our world works. Thank you for this fascinating journey.
I can't be the only one that initially thought it was pi rotations rather than 7/2 when you counted them
Same! I was sitting here like, "do I smell pie?"
I was also thinking pi rotations!
@@sudoscoobs1373 Great. Now I'm hungry.
same, it's a very likely place for pi to come jumping at you 😁
Sad to say I didn't think of that. I was just confused at how the heck 7/2 seemed to appear.
Would be cool to mount the top-down camera to the turntable so it rotates with it. When you mentioned the non-inertial reference frame stuff I was hoping to see the ball’s path from that reference frame.
Yes, I very much am interested in that. My intuition is that it's elliptical orbits that resemble orbits due to gravity. Though, maybe it's more like anti-gravity since the force on objects is outward unless they can roll.
-Look up hypocycloids, they are star-like shapes that form if you trace a point on a small circle rotating within a larger circle. I think the ball's path from the table's reference frame would be look like one, with k=3.5 or 7 points to the star.-
EDIT: this is wrong, it will just be a spiral that moves inwards then outwards and joins up with itself
its possible to just stabilize the video on the turn table, if someone wanted to put in the effort.
@@dustinandrews89019 he mentions in the video that it cuts a perfect circle in vacuum without slippage, and a spiral with slippage.
@@mrjbexample spirograph?
Seeing you advertise "The Länd" took me by surprise. I didn't know we were advertising internationally. Also, your pronounciation of "Baden Wörttembörg" is really adorable. 😄
Nett hier aber waren sie schon mal in Baden-Württemberg?
LOL was about to stop watching the video but now I’m gonna keep watching
The hollow ball discrepancy blew my mind. And the seeing the mathematical proof was so satisfying. I love when maths describes real world phenomenon so comprehensively.
as soon as you brought up a hollow ball and I saw the numbers 5 and 7 pop up, I thought of Moment of Inertia. I am pretty proud of my tiny noggin for thinking of that
same. I also thought at Cv and Cp of ideal gases but then I excluded then because of the context (though, it's still spinning stuffs and inertia ;) )
Noggin! Now that’s an old word! Mate you’re showing your age! 😂
@@RestWithin i am probably younger than you think haha
@@MyriadCelestia atleast 80
It is precisely related to the inertial moment, confirmed if you examine the paper. We try to express the equation as: I = k m r², with k = 1 for hoops, of course.
We have a lab the student do that rolls different types of balls down a rail of variable separation and they have to predict the speed in terms of the "k" value. It's very enlightening.
As a lab, this would be equally fascinating.
Your videos are simply awesome
Very helpful
Thumbs up
👍
Hello verified user
Very good
Would have loved to see a view locked to the turntable's rotation (i.e. a camera from above rotating at the same speed, or each frame rotated to keep the turntable apparently in a fixed position). Bet the ball movement would look pretty interesting.
This would be great!
Also this video's a decent explanation of orbital mechanics, where poking it inward to where it's moving faster etc
Seems simple enough to deduce what it would look like. For the ball staying in the spot, it just describes a circular orbit for the table. For the ball going in a circle, it would be an elliptical orbit precessing one seventh with each turn, so that after seven orbits it ends up where it started again. Or five if the ball is hollow.
@@davidwuhrer6704 it's not that I can't figure out what it would look like, but it would be enjoyable to see.
@@batlin That it would be.
Love the video! Wanted to say, I did my master's thesis on how students conceptualize the Coriolis force, and I'd recommend avoiding terms like "fictitious" when describing it. It gives students the impression that it's 'made up' or 'doesn't exist', which conflicts with their bodily perceptions which have experienced the force first-hand. Also, it makes it sound like it shouldn't be trusted (let alone, used), rather than emphasizing how helpful (and necessary) the Coriolis force is when viewing things from a non-inertial frame. Personally, I try to call it an "apparent" force, because it 'appears' when you change your perspective to the non-inertial frame. It's all about clarifying the contexts in which the Coriolis force is productive.
That's a really good point, thanks! How about virtual force? I quite like "apparent" though.
@@SteveMould you could call it the Coriolis effect
@@SteveMould One of my hobbies is long range rifle shooting, so as you could imagine, the Coriolis Force / Effect becomes a factor in my accuracy. When you said "fictitious force" in the video, I definitely raised an eyebrow before I reminded myself that centrifugal force is similar in not being a real "force", because I have definitely witnessed the Coriolis Effect. I feel like "fictitious" can cause a knee jerk reaction. I think "apparent" would fit perfectly, or simply referring to it as the Coriolis Effect, as that does not imply any "force" is being added to the equation.
@@SteveMould Especially since Flat Earthers will use it as "proof" that Coriolis effect isn't "real". Apparent force is much better. Same for Centrifugal Force.
@@SteveMould "emergent" is often used to describe effects which are not fundamental, but arise as a consequence of other more fundamental effects.
This helps me visualize how a Lagrangian orbit can be somewhat stable despite all the forces being apparently unblanced.
Good point.
Yeah that's kind of how JW telescope keeps orbiting around it's lagrangian center. Although its path is an 8 figure rather than a perfect circle. Which make me think that this 8 figure (lemniscate) might be a 3D substitute for the 2D circle. But idk
The sky is not "outer space". Sorry to break the sci-fi illusion. "Gravity" is a pseudo-scientific belief about balls of matter in the sky.
@@pineapplepenumbra,
Good Lagrangian point.
That's exactly what came to my mind immediately when he showed the circular orbit of the ball that doesn't go around the center!
I saw this at the Experimentarium, a Science Museum in Denmark. One interesting variation is a large hollow ring (a thick bracelet or similar). If you put it on the turntable vertically and let it get up to speed, and then place a ball inside the ring, the ball inside will stabilize the motion of the ring, and behave quite similarly to a single ball.
As a physicist, this video is pure joy. Thanks for making this video available, Steve ❤️
Most of us would, I think, be surprised to see a ball on a turning turntable basically staying in one spot. Instead of explaining with formulas only, you described how it happens very simply. Great work!
Amazing video.
I have a doctorate degree in Physics and I am always amazed with your videos. Kudos and thanks for the link to the paper.
Very good at cutting out the technicality and still keeping the explanation satisfactory
Your videos are simply awesome! I am a rerired Physics Teacher and could have used your videos to engage and challenge my students while I was teaching. I never miss your videos and thank you for keeping my love of Physics alive and I hope inspiring a whole new generation of young students to take up the challenge of physics and science in general.
your videos
I started chuckling to myself the second I saw the equation for the moment of inertia of a ball. This was so cool! It's nice to see some interesting physics can still be done with closed form equations.
I’m curious. What is your thoughts on open and closed formulas relative to physics?
@@lukedowneslukedownes5900 Equations are closed, formulas are open.
@@lukedowneslukedownes5900 by closed form equations they mean that the equation can be solved analytically which generally leads a nice solution. Otherwise you have to solve it numerically.
@@ratulxy It helps that your post was good, but I thumbed you up before I read it, just because your name deserves it.
@@pineapplepenumbra haha, thanks!
I really liked how the equations are presented here. Must have been a ton of work. Thanks for making the effort.
You keep fascinating us as well as entertaining. Thank you for that Steve. And congrats to those, who choose you to promote "THELÄND". Perfect choice. I am from Germany and have seen the clip before. And yes, I believe for tech or science aspiring people, that is a perfect place to go to.
Yeah I loved that his sponsor was a state of Germany!
I imagine the formula for the motion of a slightly elliptical ball would be terrifying.
I am getting nightmares already.
It can’t hurt you
yesss ua-cam.com/video/bMxMubVq350/v-deo.html
The truth is that any real world ball is already slightly elliptical, since perfect shapes are nearly impossible to create
@@shadowcween7890 why are u saying nearly
I love how you can see the line bent with the rolling shutter effect when he pauses the video. So cool
this part 3:08!
This was such an interesting video. I don't remember any of my alevel physics but I do love stuff like this
I like that you showed some of the math here as well. I think too many youtube science channels forget that besides just describing observations we also already have a lot of very good models that can predict the observations very well.
A ball rolling from a flat surface, onto a turntable, back onto a flat surface, is also interesting. It swerves on the table, but exits perfectly in line with the direction it entered from.
Modern scientists: it exits perfectly in line with the direction it entered from.
The line in question: 5:32
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Know that there is power in the name Jesus Christ! His name casts out demons and heals!
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I too, was a wicked sinner of the world before I opened my heart to God. I am living proof of God's work and fruitfulness! He is an active God who hears the prayers of his! God's children are set apart (holy) and righteous. The devil is a liar that comes to steal, to kill, and to destroy; that includes your relationship with God.
Open your heart to God, repent of your sins (he will forgive you), and let him direct your path. Draw nigh to God, and he will draw nigh to you. Cleanse your hands and purify your heart, lest you walk with the devil and follow him to hell.
Classic Mould. Breaking an interesting phenomenon down to easily understandable parts. It makes me feel smarter than other channels because it's like he is just making me realize what I already know opposed to teaching a whole new concept.
Also very willing to admit he doesn’t fully understand it either. Humanises him. Great guy.
OK
´been listening to this half asleep and it’s so brilliantly narrated that I’ve recorded the video in the watch later list. Steve is one of the very few best science sources on youtube and better than very large institutions that allocate large sums of money into it. Steve has the knack of finding sufficiently mundane stuff that anyone can relate to, yet is scientifically relevant and catchy. Steve, you’re the boss. Thanks a metric ton.
Ok dude, you've grown on me and I love these videos. Thanks for getting on with it and having the balls to just make the videos!
It's always delightful when a simple experiment reveals unexpected behavior.
Watching this video almost 40 years after I dropped out of taking Physics and Maths for A-level, I'm glad I did. The overlying description of what's happening is utterly fascinating, but the calculus, the physics, the number-crunching... it was never going to be for me. I absolutely LOVE the passion you and others have for such things, because I have my own 'things' which give me joy. Glad to be a viewer, amazed to catch of a glimpse of something described in a way I can understand it, knowing that you can do the maths and the physics and I don't have to!
There was a time around 6th-8th grade learning high school level algebra with a very good math teacher that I really enjoyed it mostly because the teacher made me understand it and therefore I was really good at it and had really good grades as a result. Fast forward several more years and terrible math teachers later and I was never able to successfully advance past that and had terrible math grades by the time I got into college.
Lol I'm the opposite.. didn't drop out and got a mechanical engineering degree and lots of regret
@@occupyallthethings can you elaborate?
I am a first year in mechanical engineering and maybe i could get some insight
this is a typo and you meant to say 4 right?
ok
Your 'paradox' videos are my favourite ones, Steve
Centre for Life in Newcastle had a massive turntable (not sure if it still does) with lots of objects you could experiment with. We practically spent all day on it it, it was great fun. 😊
I swear you always come up with the most mundane topics that slip right by the rest of us, and yet are so very fascinating when you take a closer look at them. Another amazing video.
When I was a kid, the Fort Worth Science Museum had a 6-ft radius stainless steel turntable set flush in a table so there were no pinch points around the edge. They had all manner of round objects for kids to play with. I remember my parents saying it was time to move on, but I was mesmerized playing with wheels and balls on the spinning table. Good times
This was so nicely presented. Great video.
Wow, amazing video!!! Love your work, the experiments and the clear explanations.
Amazing video, as always! I've never commented here before, but I'm a long-time subscriber and wanted to say that as a researcher in physics, your curiosity is simply an inspiration to me! Also, I love your plug for THE LÄND (Baden-Württemberg), which is where I did my undergrad. It's a great place for Science indeed!
Let me guess, Heidelberg?
@@danielsieker9927 That's right!
Just realized you went from finally hitting 1M subscribers a few months ago to being on the verge of 2M right now. Well deserved! And as always great video :)
Right.. because it matters.
@@ShainAndrews Jesus! Op just congratulating him on his success. And, idk about Steve, but subs number matter for a lot of youtubers considering that's their livelihood.
You’ve done a great job of contributing something for all of our benefit.
Dude, the math explaining the 7/2 was so beautiful. It made me smile!
I don't think I've seen a Steve Mould video I didn't like, but this might be my favorite. I was slack-jawed in surprise for a lot of it. The way the balls moved really was unexpected and quite pleasing as well.
Would love to see a camera view mounted to the turn table. I assume the the ball would appear to trace a pattern like a spirograph.
I got a nausea from this idea
maybe have a sensor inside the ball
As soon as I saw your comment I knew I had to make it happen - Here's a handful of shots from the video that I tracked, and one shot that I traced the path of the ball, I put my thoughts about it in the description under the video (unlisted, but still sharable) - ua-cam.com/video/-iQJmPo1tTs/v-deo.html
This was simple enough to understand, interesting, and informative af 👏 👌🏿 👍🏿 subbed.
amazing! perfect blend of well delivered info-tainment! didnt know what I didnt know.....yknow?
Wow, this takes me back to the 50;s. We had a record player that didn't work (the audio didn't) but the turntable would spin. We'd put on a 33 LP and put a marble on it. I observed the same results as you did but had no understanding of the physics/math involved. Thanks for the excellent explanation,
BTW, we would also roll up a paper cone, stick a straight pin through the pointy end, and hold that on a record to listen to our tunes. Way cool.
Just sane... :^) Saint
Me too but I used a CAT. 😆
@@richardchambers256 Ha! 7 to 2 ratio, 7+2=9 :lives. Coincidence? I think not. He he he...
I did this when I was young as well. The paper needle trick works with a flat paper or cardboard already but slightly quieter. Though the best thing always has been to choose the wrong speed 😅
Dito
My little sister and I used to use an empty dog biscuit box and a needle to listen. 😀
I love that at 3:20 we can see the rolling shutter make the line curved
This has such great timing, for me, as for the question I had in my mind, about the Harry Styles , Music Video, As It Was, music clip has him walking 🚶 or running 🏃♀️ around on a turntable, although with another blue,red vector possibly. However where I am going with this had answered a question for me, thank you. 🎊 😊
Very nice explanation. Excellent. Explained as simply as possible. ♥️
I like thinking about your videos like they're a published study in a scientific journal. Love the idea of the conclusion of a paper being, "Balls and other round things behave weirdly on turntables."
0:52 thanks for the ball to hand size clarification here. 🤣
They are not normally that size?
Nice demo. The 7:2 explanation particularly good.
Steve Mould is the perfect example of how to make science interesting and engaging for the laymen and encourage curiosity. Asking questions about even the most mundane of observations and interactions is invaluable. We don’t know what we don’t know until we ask why and how.
I would like to see an Eulers disk spin on a spinning turntable. Once when the disk and the turntable both rotate in the same direction (e.g. clockwise) and once when one rotates clockwise while the other rotates anti-clockwise.
@@Nicegram_SteveMould001 You are a scammer. Messages like these are cropping up all over UA-cam.
The people have spoken!! These are our demands, our balls are in your court!
Fascinating stuff, very well framed in images and clearly explained. Thanks for your video!
Just found you today.... I'm an instant fan!
Really cool video, thanks for teachin!
I've seen this done with an umbrella as a bit of a parlor trick - good to understand how it works
That IS a cool parlor trick!
Hi Steve, there's lots of fascinating ideas here that would be cool to explore. For example, if the spinning surface was curved like a Euler's disk, how might the motion differ compared to that of the flat or convex surfaces? Here you present flat, and earth is our convex. This harkens back to your "this should slip off but it doesn't" video with spinning concave and convex surfaces and a spinning band. Love the videos and making us foster unique concept connections!
When I saw this I was reminded of Lagrange points and how objects near them have stable orbits around them even though there's nothing there. Of course it's the same - another example of the Coriolis force. Great video, thanks!
this was very interesting to watch, thank you.
Brilliant stuff, as ever - loved finding out where the 7:2 ratio came from!
I'm so glad you mentioned something about coriolis. That's kinda where my mind went watching the ball go from closer and further to the point of rotation.
Not only that - when I see the ball orbiting around a point, it reminds me of a moon. Almost as if it does not even need a planet to do such movements, or, all the planet does is give the cause for the orbiting moon to orbit another center.
@@feedingravens except, the moon isn't rotating on its own axis is it? Planetary satellites orbit their hosts regardless of their own spins. Hmm...
ok
@@truongtran-sl6rh alrighty then
@@feedingravens idk... Remember, the center of orbit between moon and earth isn't the center of earth.. so their orbit is a relationship between the two. The reason it's tidal locked with earth is also that reason.
Adding friction to rotating bodies it completely different than orbital mechanics. As I know of. That ball is experiencing different tangential speeds as it moves closer and further away from the axis. Orbits do have a sling shot kinda effect. But I see that different than this. But I could be wrong.
could you use this setup to experimentally calculate the moment of inertia of a spinny thing with an awkward shape?
Bravo! Brilliant! Subscribed.
Did you make or buy that motorized turntable? Just typing in turntable gives the DJ turntables and I would love to have one for my classroom. Awesome videos. I embed many them as supplemental videos to watch for high school physics.
He is using a pottery wheel. Check with the art department?
yeah, that's totally a potter's wheel...
Lol
Watching the ball on the turntable is mesmerizing!
I must say I fell asleep why watching your video and it was the best nap in days. Thank you and you voice. I must rewatch the video :-)
The contact point on the turntable, if not assumed to be a point but rather an area, would be roughly circular and the radially outer portion of it is rotating faster underneath the ball than the radially inner portion of the contact area. But the circular contact area on the ball which is rolling tangentially cannot be faster on the radially outer portion compared to the radially inner portion. So this would induce some slip i assume cause the ball can't start to rotate about a vertical axis when it is already rotating around the axis that allows it to roll along tangentially.
I think you can see the toy car affected by this and turn slightly left
Love this one. Glad you mentioned the Coriolis effect. When you showed the gyroscope, I thought you were going to talk about procession. That would be a good concept introduce here too. By the way, your videos are great!
Adam
You've got me visualizing a parade of gyroscopes dressed in fancy costumes.
Loved the emphasis on intuition in this video. Don't think the lesson/insight could have been taught better 👍
Watching this after taking physics and this actually makes so much sense. This is actually very similar to rolling an object down a ramp, and that’s where the 7/2 ratio comes from The moment of inertia times the lever arm.
I guess you failed physics then.
@@johnsomerset1510 got a c-
Very interesting experiment. Thanks for posting it.
I'm glad to have found you... purely because your videos make me remember my curiosity as a kid. The things you lose when life takes over! Great going!!
As a 70 year old chartered engineer I am always learning new things. I had never seen this before, so thank you.
Absolutely SUPER GREAT video. Thank you.
I'm interested if a similar effect would occur with other solids of constant width. Really cool video, as always, and I enjoy learning from them!
So strange how our intuition of where the ball goes kinda depends on the ball realising it's on a turntable and behaving accordingly.
I loved that point of your explanation.
The circular motion of the ball reminds me of the motion of an object in space orbiting a planet. If its orbit isn't circular it gains velocity as it decends, and then exchanges that velocity for altitude after periapsis.
I have probably played too much KSP.
I wonder if this is related to how the James Webb space telescope has that unique orbit?
Steam says I've played KSP for 3,310 hours. And yet, when I get home tonight from work, guess what program I'm gonna fire up...
He has a video on that exact thing. Or at least I've definitely watched a video explaining why the orbit of planets and bodies are all evenly balanced because of oval orbits since it's extremely rare for an actually perfectly circular orbit due to universal gravitational pulls. This results in all orvits eventually balancing at a certain point in the oval which can lead to interesting alignments on very rare occasions which I'm fairly sure was him since I don't watch many other channels like this but I could be wrong..
Unrelated
Fink dat so
Steve, this is very fascinating. I really appreicate. I am guessing that, near the surface of the turn table, there is general tendency for the air to flow from the center of the turn table towards the edge of the turn table. The reasoning is that the surface of the turn table moves faster as you move from the center of the turn table towards the edge of the turn table, and, thus, air moves faster as you go from the center toward the edge of the turn table, which, in turn, means air pressure becomes lower as you move from the center towards the edge of the turn table. I thought it would be fun to observe and analyze the roll of air flow near the turn table surface and around the ball.
Also, I would really love to see you conduct the same experiment you did in this video in vacuum just to see whether it makes any difference.
Mind blowing! I absolutely love this!
Sounds like a way to understand precession and LaGrange Points. There's something deep about gravity and dynamics in this demo, but I can't quite crystalize it. Any ideas about that, Steve?
I have always found spinning things and reference frames fascinating, and as an English teacher, I find it fascinating that these very real forces are referred to as fictitious forces and pseudo forces and imaginary forces. I suppose it is to separate them from contact forces and EM forces, but it does seem odd to me. I read that even gravity is a fictitious force. If there's one thing we can be certain of, it's the force sticking our bodies to the floor. Very interesting video and very clearly explained. Thanks.
Fictitious forces are not real forces. They do not actually exist like any of the fundamental forces (e.g. electromagnetic or gravitational), but they are very much necessary in order for someone in a non-inertial (i.e. accelerating) reference frame to explain what they are experiencing. As an example: you are a passenger in a remote-controlled car that is moving at a constant speed in a straight line. The car has no windows and has absolutely perfect wheels, shock absorbers, etc. such that you cannot even tell you are moving. Unfortunately, you are also not wearing your seatbelt. All of a sudden, someone turns the wheels sharply to the right via remote control. You will go flying into the left side of the car. From your perspective inside of the vehicle, you have no way of knowing that someone has caused your car to turn. From your perspective, there was suddenly a violent force pulling you into the side of the vehicle. What force has caused this experience for you? In reality, there was none, however from your perspective it must have been so, and so we would attribute (from your perspective) a fictitious force called the centrifugal force. Hope this helps!
@@HouD I do appreciate the answer, but try saying 'in reality, there was NO force' to someone who was badly injured or even killed by such a force. Surely there was such a force, and not just from his perspective - from our perspective too.
And why have I read that gravity is also 'a fictitious force'? Is it because relativity claims (and I certainly can't understand the logic) that gravity is just a curvature of space and time? I have no idea!
The difference between fundamental and fictitious forces is that if you change your perspective on a fictitious force, you can make it go away (in the sense that they’re no longer terms in any equation), and things like electromagnetism will exist in every reference frame.
From an English major point of view - picture something like Fight Club. Tyler Durden was very real for some of the characters’ perspectives and even produced real outcomes for them, but was still not real.
@@MrSkypelessons don't conflate the force that might injure someone (e.g. the contact force as they slam into the door of the car) with the perceived force that attracted them towards the door in the first place.
We would not label gravity as a fictitious force. However, yes, in a very thereotical sense gravity is not a force like a push or a pull. However this has to do with General Relativity and advanced ideas in physics. For your (and my) every day life experiences, gravity is very much a force that pulls massive object towards one another.
@@HouD 'We would not label gravity as a fictitious force' - who is we?
'This led Albert Einstein to wonder whether gravity was a fictitious force as well. He noted that a freefalling observer in a closed box would not be able to detect the force of gravity; hence, freefalling reference frames are equivalent to an inertial reference frame (the equivalence principle). Following up on this insight, Einstein formulated a theory with gravity as a fictitious force and attributed the apparent acceleration of gravity to the curvature of spacetime. This idea underlies Einstein's theory of general relativity.'
You explain things so much better than Veritasium, which I greatly appreciate.
Thank you! i love the content and straight to the point video! keep on going! Sub from first video!
Nett hier, aber waren sie schon mal in Baden-Württemberg
Nett hier. Aber waren sie schon mal in Baden-Würtemberg?
The moment you mentioned it was a different, but nice number for hollow balls immediately made my mind jump to moments of inertia
the first two minutes of this video is pure magic, not a single second i got something i expected
As someone who's been putting marbles and ping-pong balls on turntables in the name of Sound Art for the last 10 years, this video was very useful.
What are those sounds used for?
@@andregon4366 I use ping-pong balls to semi-randomly trigger synth sounds as part of a music performance: ua-cam.com/video/_p0CGOoN7J0/v-deo.html
Nett hier.
Aber waren Sie schon mal in Baden-Württemberg?
Ok the disc example now has me wondering how a Cyr wheel would respond to a rotating platform in various types of motion (rolling vs coining vs waltzing).
Understanding Rotational Dynamics has always been interesting and pain in the neck at the same time.
I believe without doubt that there is that fixed ratio because the other factors cancel out, but that being a different constant for hollow balls is really weird. At first glance, it makes sense, but what if you consider the thickness of the ball "shell" as a fraction of its radius? Now you cannot discretely differentiate between whether a ball is hollow or not (or rather, solid balls become a special case of hollow ones), because at the limit→1 they are basically the same
if I'm understanding your comment right, basically the ratio for that hollow ball isn't exact. The ratio is for a theoretical ball with infinitely thin walls. A more complex equation exists for a solid ball with a cavity.
As you change the distribution of the mass by hollowing out the middle you make a gradual transformation from solid to a "thin shell". Of course, where do you draw the line at "thin"? When the assumption of a "thin" shell is good enough.
There's this very hands on science museum in the SF bay area called the Exploratorium, my favorite museum as both a kid and an adult. They had an exhibit about this which was my favorite thing there. It was a giant turntable, like 4 feet-ish in diameter and a ton of discs and balls of different weights and sizes and some of the discs had holes in different orientations. I could easily spend my entire day there just playing around with the physics of it, trying so hard to get one to stay on for as long as possible.
was going to mention exactly this, but you beat me to it. :) I've spent lots of time there, too... they also have little sticks that one can slide through the holes in some of the discs, or also some rings, to allow them to be held still to set up. Another fun thing is rolling something onto the turntable from the side, as the turntable is basically an inlay on a larger table surface, and the heights are flush to each other... so you can roll a ball on at different angles, and see what it does as it transfers from the static table surface to the dynamic turntable surface. Much fun! Highly recommended to anyone in/around (or visiting) SF.
I lived near SF from around 1980 to 1991. That was when the Exploratorium was still in the Palace of Fine Arts. I became a member and visited often. This exhibit was originally intended to show how something on the turntable would be flung off tangentially to it, not straight from the center. But the objects were small disks, and everyone found seeing them roll on the turntable was much more interesting.
Getting pennies to roll was fun, too. I don't remember the museum having spheres of any kind for the turntable. I never thought of bringing a ping-pong ball.
The most interesting object I saw there was one of those rubber feet for folding chairs or canes. It's shaped like a cone with some of the pointy end cut off, and the bottom was somewhat rounded. A rubber sink/bathtub plug could've be interesting to watch, too.
@@JimC Aw I miss that location. It was so much more open than it's current place. You walk through the doors and just as far as you can see there were experiments and things to play with. It's a lot more moderny now, which is fine but it did lose that sense of awe it used to have. I used to go to summer camp there when I was a kid and we would have an hour before it opened with all the exhibits turned on to play around with. Easily the best summer camp experience I can remember.
@@playr4 Sounds like lots of fun!
In Chicago, back in the 60s, when I was around 11, my older brother worked on Saturdays in the Museum of Science and Industry for a time. He worked in the Swift exhibit (hatching chicks, tending a sheep or two and a few baby pigs). I'd usually go with him (if I didn't oversleep :) ). I couldn't go into the museum proper until opening time. But then I'd hightail it to exhibits that were usually crowded later in the day and wander around until closing. I loved it!
The Museum has changed a *lot* since then, but if you're ever in Chicago go see it!
@@JimC interesting about the intent. I don't recall what their signage says on it these days, but I know they've had billiard balls among the other options. The rubber feet sound interesting!
I though I've seen it all.
More surprising than anything else in this video is the fact that I just witnessed a sponsor spot about my state in a Steve Mould video.
I did NOT see that coming haha
I had an amazing realisation about this and have a completely new way of looking at it!
This situation is perfectly analogous to the case of cyclotron motion in a magnetic field. The rotating tabletop takes the place of the vector potential and would yield an analogous vertical magnetic field. The ball then is like a charged particle.
While Veritasium's 'sliding finger under cane' video became popular that it ended up being asked in JEE Advanced 2020 ( I know there were a few research papers on it beforehand)
This video has the topic which is favourite of professors at IITs for framing questions...
I m gonna take a note 😁
Thanks Steve
Which video, may I ask?
@@subhadityanath4326 ua-cam.com/video/jIMihpDmBpY/v-deo.html
Veritasium explains here the sliding finger under cane phenomenon ( why always both fingers end up right below C.O.M.)
And kind of same question was asked in JEE Adv 2020