Finding the center of mass
Vložit
- čas přidán 18. 05. 2015
- This is a quick explanation for finding the center of an object's mass when the object has a consistent thickness throughout one dimension. The push-stick can be thought of as two-dimensional in a sense, because the plywood is 3/8" no matter where we measure it. Because of this uniformity, z values will always be the same; thus, the center of mass is the average of all x and y values that the object occupies. The mass isn't really "evenly spread all around the point," so much as the point is the average location of the mass. Technically, the point is really inside of the wood, half-way through its thickness, but let's try not to get too lost in the details ;)
This trick cannot be used for every object in this way. Objects without constant values along a certain axis may have centers of mass that are located inside of the object, or even outside of it and off of it completely. Think of a horseshoe as it rotates through the air while spinning: Where would its center of mass be?
The push stick featured in this video is a handy little wooden device that is used to keep your hands safely away from a blade while using a table-saw. A print-out for making one can be found at John Heisz's website. Here is the related video:
• How To Make THE BEST P...
I recommend the design.
Oh, almost forgot: I put some extra content on a second channel. The link to it is on my channel home/about page. It may not interest everyone, and I don't like the second channel trend either, but there is a reason, so cut us some slack: It is nice to stretch the legs of creative autonomy, and nasty comments have a tendency to stifle that. Lowered expectations allow me to take risks, and that is appealing. Well, check it out. You may find something good there. Uploading almost done... so, hope you like it, and let me know if you did! - Jak na to + styl
I'm gonna have my center of mass tattooed on me. I just gotta decide where to drill the holes...
You need Jesus...
He knows about where to be hung up by holes.
OminousPineapple savage.
You have 69 likes right now... Just so ya know
@@OminousPinapple I am dead . You win youtube comments XD
As always, very interesting!
Now that's a push stick:)
John Heisz Thanks, John. The plan for it is only $2.99 if you want to download a copy!
Just kidding. I put a link at the end of the video for you. Glad you watched ;)
John Heisz That's a flippin' push stick!
Boring af
Whoever you people are who liked this in the first two minutes I posted it are awesome! Sorry about the re-up.
I'm going to work out the centre of mass on my swan neck push stick around this weekend, and then throw it around. Great video!
I think I realize why I like you better than other CZcamsrs. Your work makes me think, but it's also interesting. It's rare that intellectual and interesting mix in my experience, but I've been hooked on your videos.
I've said it once and I'll say it again, I've learned more watching vids like this than when I was at school. Great stuff mate and thanks
I love your videos Pocket, I've never really been very big into wood working, but you have a voice and a personality that makes it impossible to stop watching. Keep up the amazing work.
Very succinct. Thank you for the new perspective. I could see how this could really help with planning a balancing sculpture.
I love your videos man keep creating you share so many great tips and knowledge thank you!
Your videos are always interesting.
That was very interesting, thanks for putting in the time to make this video, I really appreciate it...
FRICKIN' SCIENCE, BRO. Thanks for the video(s), really did seem interesting. As unintellectual as I am regarding physics, your videos are always fascinating and informative. Just another subscriber to support you til' the end. Even by then, haha
Emman Pascual I appreciate it! Glad it kept your interest.
Thanks for redirecting my view point on objects. Great video.
Great video. I love information. Keep up the good work.
Wow! What a great video. So well explained and thought out.
This inspired me, thank you. Laminas, centroids, and center of masses are cool to learn now.
Great video it was interesting and explained very well. Thank you for your hard work.
This was brilliant and I loved every bit of it.
Best Wishes, Brendan.
baconsoda I'm glad you liked it. How is it that my bizarre content and nasty commenting habits haven't driven you away yet? You must be a glutton for punishment! I really do appreciate the support- thanks.
pocket83² I like people who don't feed me bullshit and that I think I can trust so I like you.
excellent explanation man that helped a lot !!!
Thanks for the video. I learned something new. A simple effective method to find c of m. I wish I had some geometry teachers like you when in school.
This is awesome, I just shared it with my woodturning group.
Thank you for the educational video.!
I remember being fascinated with this method as a kid after seeing it in one of Martin Gardner's books. Thanks.
Thanks for this... useful stuff!
Been wanting to know this for years... Thanks
Learned something new! Thanks
Wow, you're a young version of "Ask Mr. Wizard." I learned more watching his Saturday half-hour TV show than I did in a month of ossifyingly-boring science classes in school. BRAVO!!!
Thanks man! This was helpful!
You are so awesome! U helped my physics hwk so much!
thanks, very cool, clear, educational
Thanks alot for this video ,it helped alot
Cool!
It was interesting. . :-)
Awwww... i thought your second channel would be harder to find. I thought the clue was the Pixel image in the background of some of your shots (the dark green one holding a ball). I even took a screen dump and used google image search to try and find it because i didn't recognise what it was...
...and it turns out that the link was in your signature.
BTW, your channel is awesome :-)
So that's how one finds the center of mass (besides trying to hunt for a balance point). Very interesting.
Ahhh....a tingling in the grey matter I rarely need to use at work. :) Thanks!! Very nice!
Neat concept!
Nice explanation
Really good description and instruction. (Did drilling that third hole SLIGHTLY shift the center of gravity by removing some material on one side of the center lines?)
Jeremy McMahan Of course it did. But how far are we taking the details here?
It was more of a theoretical question than one of practicality.
Jeremy McMahan I gotcha ;)
Tnx man! That was indeed very interesting!
Nerding out!
Keep up the great videos :D
Dinofuzz11 I will try! Thanks.
No problem! Your works have been very inspirational and you explain physics and just simple concepts very well in your videos
that is so interesting! well how about the center of mass of an irregular shape varies with change of radius? can you help me on this one please
Well done...
Great video Pocket
Awww the second subliminal message I've caught watching your vids. What did the shot of the chrome sphere mean in the, for lack of easier words to type, soccer ball puzzle video?
I really enjoyed watching that...I haven't a clue why! I´m not sure that I will ever have the need to find the centre of mass ;)
Interesting, and when I get information in this format it sinks in, just the way I learn.
Thanks!
I like your video!!!
Thank you.
Great Video. Now I understand how I might have tackled one of the problems on my college physics exam some 42 years ago. " where is center of mass if the earth were made of half lead and half wood" . Duh get the string.
neat trick
Super demo
great way for finding single hang point for a mobile. one that is made from say a piece of drift wood. or curved branch.
I fucking LOVE science! An another winner from you!!
Thanks for sharing this informative video.
What if the mass was not evenly distributed amongst the object? Would this method still work?
dporiua Yes, it will
dporiua You won't be able to mark it with that red pen.
Thank you
U should be a geometry teacher cause ur too amazing with crafting
Nice vid
0:44 SNES Nostalgia, never forget!
What do you do for a living pocket? Just curious as you seem very scientific, and very practical at the same time which leads me to think you studied physics at some point.
Awesome.
This was interesting.
so... what must i do to get you to make me one of those metroid upgrade stations at 2:10? would prefer a super metroid one...
Thanks for the video.
If you used a reflective sticker or used a strobe light (at night) the parabola and C.O.M. might be easier to see.
Lyonhardht Great idea, but I am NOT re-shooting any scenes for this video! This one was supposed to be a quickie, and it turned out to be a nightmare to film.
Why did it take a CZcams build video to teach me more than my Math teacher ever did?
hizo64HH Because he is actually teaching you how to practically find the center of mass on a real object, where as your math teacher was trying to teach you how to theoretically do so on an imaginary object. A lot of people are better with practice than theory.
Digging the Chozo Statue, did you make that or get it somewhere?
Josh Rowlison That is made from Perler beads. Possible future update to wood, though.
Ah, I should have looked closer, I did a lot of Perler bead fractals as a kid, nothing that cool.
I wonder if resin encased Perler bead pixel art has been done much.
Digging the chozo in the background.
Thanks for the video. It is going help me in my exam
love it
Hey pocket, you might be interested in a piece of software I've been playing around with. ProDad ReSpeedR emulates 1000 fps and creates some incredible slow motion footage with what you have (even filmed at 30 fps). Just thought I'd share, in case you'd like to do some more slow motion.
VIDEO INTERESSANTE.
FISICA/FALEGNAMERIA.
SALUTI
SALVIO
When i was a kid i started thinking about phisics when my father gave me a piece of wood whose center of mass wasn´t a part of the piece. The piece of wood you show is preaty much the same shape.
Where did you get that tuning pin from?
GeneralSeptem Nice catch. But since you know what it is, it would be fair for me to assume that you know where it came from. It works perfect; it's heavy, symmetrical, and it has a hole through it. I was thinking of making a Pachinko type game out of them.
technically, by drilling holes, you changed the center of the mass of the stick very slightly. So you could say that you changed the outcome of your test by measuring it.
Technically, the flaws inherent to any experiment don't end:
Red Sharpie ink added mass to the object. The knot on the plumb line affected the outcome of its position. Atmospheric conditions that day altered the moisture content of the wood, causing it to become slightly different from the day before. Sunlight, wind, and heat slowly erode the plywood, knocking agitated molecules and individual atoms away from its mass, in a slow but endless process of diffusion. Spherical aberration of the camera lens (and human eye) makes it impossible to capture a parabolic path and then relay it to a planar screen. My breathing altered the result. Oh, and then there's relativity, and that whole mass causing a dent in space-time thing.
Welcome to an imperfect world! Thankfully we can express ideas conceptually, and not always remain beholden to ideals, like perfection.
I see you corrected the statement about mass being equal on all sides of the center. Not to be picky, but the shape made by the object thrown at 0:23 is y=-x^2, not y=x^2.
***** That's not being picky, that's kind of obvious. But at an introductory level, I think it is good enough if they can make the generalized association of x² with a parabolic shape. I hope I don't get sick of explaining these things. One thing is for sure, I'm never making a physics video during a hangover again.
pocket83² I'm always so reluctant to offer criticism when not face to face no matter how constructive I consider it to be. Sometimes it can be a hornets nest, you took it really well though. I have seen all your videos and based on that I assumed the omission of the negative sign was accidental or for simplification purposes, and not due to a lack of your knowledge. Anyway, love the vids, especially the easter eggs. Keep up the great work!
***** That depends on how you define you coordinate system. What is there to say that the arbitrary direction called "down" in the physical world needs to correspond to decreasing values of y?
Gameboygenius You're right. There is nothing that truly designates North as "up," either; it is just the agreed upon standard (by a mostly northernly biased people). But we need our standards to communicate effectively. ***** was pointing out a useful possible criticism based on convention, and that is important to keep me on my toes. In fact, I had to take the first version of this video down because of an error in the dialogue.
But what are the little cubes for?
Majoofi Visual interest/appeal. Also to confuse the Easter-egg hunters who were so sure that the Yellow-pine cubes must be illusory.
But how do you find the center of mass for a non-uniform object, or one that has three dimensional features?
Insederec Finding the center of mass on one face of it would be basically the same. If you wanted to find the center of mass of the object in three dimensions you'd need to do this on multiple faces and connect the centers of mass on opposing faces. They'd all intersect in the 3D center of mass, but that's a little hard to do with real objects rather than theoretical ones.
Interesting question.
Does a ballon with water in it have a centre of mass?
Sure. Everything with mass does. It might change position over time, but it's in there.
Is COM = CG?
How can we find the C.G?
1) Here on Earth, usually, sort of, yes; but a c.o.g. is more often treated as a line, or a vector.
2) Assuming you are asking about 3-D objects:
Think of the center point on a square. You can find it by simply connecting its corners diagonally. This point is called its _centroid,_ and that's where the center of mass will be for anything square that's (nearly) two dimensional.
Now imagine the point that's at the center of a cube. That point will be the cube's center of mass, through which is also its center of gravity (whenever the cube hangs from something here on Earth and thus points towards the Earth's own c.o.m.); geometrically, we can also locate this point by connecting all of a cube's diagonals, but this is the point where all of the cube's squares' centroids intersect.
In other words, you have to sort of skewer, or hang, an object along three dimensions in order to find its true center of mass. As such, in real life, finding a 3-dimensional object's c.o.m. is tricky. We can discuss further details if you're still with me at this point.
neat
Did you delete the video then reap load it?
Reupload*
Patrick Kawa Yep. I made a mistake in the dialogue.
Once you drill a third hole, you change the center of the mass.
So does adding fingerprints to it.
but you touch it all over randomly, so it is safe to assume all fingerprints cancel each other.
Hmm- not if one side's a handle! Hey, you're right about the third hole, so all three should be drilled first, but it's so small it won't make a difference that you could detect within a pencil mark.
WTF !! How did you make physics interesting ?!?!
Flopper flopper 😍
IDK how he knew where to make the nailhole
There's a beautiful video of an MIT professor throwing irregularly-shaped objects around in the dark, while their center of mass is lit up with a little LED.
EDIT: It's colored with florescent paint. watch?v=DY3LYQv22qY (1 minute long)
Edan Coll Thanks, that was a really good way to demonstrate it! My video is still better, though. lol.
+pocket83 its actually not..,
+KingWorstie Maybe _you_ should try making a video that is both informative and entertaining. You might want to work on sentence construction first, though. Good luck!
pocket83 i wonder how you can live like a normal human being when every time you look in the mirror you get a hard one from yourself
+KingWorstie Wow, sounds as though you have a winning personality! Your viewers are going to love you. Post a link when you're finished!
is the parabola the result of gravity... or is it merely density? What do you make of this: czcams.com/video/G90A2kg1bWs/video.html
Stew Pidass The parabola is a confluence of the multiple forces and mathematical principles that quietly govern our reality; it's the end result of a whole bunch of stuff, and we are lucky enough to be able to recognize the overall pattern.
As for those flat-Earthers: I don't have time to watch all of that, but from what I understand, it is just a rhetorical exercise, like when (in debate) you argue as the Devil's advocate for the sake of refining your skill in formal argument. I do that sometimes in the YT comments. No rational person would actually take that stance, but as John Locke once asserted, there will always be "idiots and children" who will not assent to even the most basic truths.
yep, found the link
Je ne vois pas le rapport avec la position du centre de gravité et le fait de lancer l'engin.
La parabole formée suit le centre de gravité et correspond au calcul y=x2...
pocket83 is pocket83² your second channel?
Lol I got the link
who noticed the chozo statue?
#physicsrocks
Chozo statue.
hmm, so that brings up the question of where the center of mass should be on a safe push stick. seriously
Tommy Evans Of course, it is one of a million possible design considerations while making any object of function. But in this case, there are so many other considerations that John took into account first, because they were _much_ more important. Successful engineering is, in general, the fair evaluation of design elements to optimize efficiency.
So then, why are we not nearing an optimum on the designs of our commodities now? Well I'm glad you asked! But I'm not answering that right now, because it makes me angry. Short answer: Now we engineer _profit,_ not product.
I'm deaf please someone explain what does he saying🙏
Hello Ilayda. He is showing how to find the balance point on a flat piece of board. Imagine a see-saw with one person heavy and one not. It shows where is the middle point
but...y = -x^2
joe chu Yes, but x² is just a generalized version of a parabola. It's the thing that you see that tells you that a parabolic shape is in this graph somehow. A negative sign is just a multiplication by (-1), so it's just a transformation to the generic "form" of it. I just wanted to keep it basic for people who wouldn't know to think about that.
i simply thought that having "y = - x^2" would make it much easier, faster, and apparent to understand
Center of mass is not the same thing as centroid.
Pedantry is not the same thing as cleverness.
Boring af
What interests you? Seriously, I dare you to answer: name one topic that I won't be able to reduce to tedious, frivolous rubble. What do you use your time for? Cars? Games? Girls? Sports? Money? Nothing about you is interesting either, and your comment proves it.
I'll tell you what gets _really_ boring: reading stupid comments.