Professor Boyd F. Edwards is demonstrating the conservation of angular momentum with the help of a Hoberman sphere. Full video - • Angular Momentum Demo:...
@Ρгοηαtoг тεηdoη yup, they radiate pretty hard, slowing the speed dramatically over thousands of years. Later then they keep rotating at a slower pace much more peacefully
@Darui blackholes don't have rpm per se, but they have an angular momentum measured as a fraction of the speed of light from 0 to 1. This momentum does not correspond to an actual rotation because BH is not an object but rather a region of space-time, which twists quite oddly and counterintuitively under the influence of rotational energy
If only physics in school I went to were taught in this passionate, sweet manner I wouldve paid much more attention. Great job, Dr. Edwards. We need many more teachers like you.
but what is the point of doing this? We can easily know what was gonna happen by doing very little math. What is the point of needing a whole example to know something which can be known in 3 lines
In our school we did this experment by a one sitting on a rotatable chair giving two weights to both hands. Telling him to keep tha weights closer and with a distant time to time while rotating. Consequently his rotating speed was increased and decreased
Short version of why this works: If you think about it, both configurations have the mass moving through the same amount of space in a second. It just so happens that when it's expanded that space covers fewer degrees of rotation as the same amount of space when it's contracted does.
@@danzoom pretty much. The Earth at the equator has a surface velocity of ~460 meters per second. When experiencing this rotation on the surface, we don't feel like we are moving because we match the earth's surface velocity. TLDR: Earth's surface moves about 1000 miles per hour, we don't feel it because we are attached to it by gravity.
To anyone who wants to know the math behind this: Angular momentum dictates that a spinning object's linear velocity should remain the same even if you change its radius. According to the equation w=V/R (w being angular velocity, V is linear velocity and R is radius), as V remains constant, the larger the radius, the lower the angular velocity.
@@sombrerocat2971 no, the burden is on those who gave enough damn about any of these comment to make thier own instead of spending the same hour by doing something productive , that applies to me too :D
goddam, you're a lucky student. i went to a v v v good state school, but state schools are generally huge and due to their state funding, they tend to have more research competent profs than profs that can teach. in my 5 yr prog (at my school biotechnology and molecular biology was recommended to be finished in 5 yrs due to having 85% of our classes be lab work) we learned all of our maths (up to calc2), physics 101/102 and inorganic chemistry 101/102 by ourselves with the aid of the tutoring center. cz our maths and physics profs were on proof grants and our chem dept was on lunch cancer and stem cell research specifically and they were all trying to show results. if this dood was my physics prof I'd prolly double major in physics too. not gna lie, physical chemistry was the most difficult theoretical course I'd ever taken in undergrad.
This is also a little engineering trick to keep in mind, since this applies to gears and levers and the entire reason concepts like torque even exist. When you draw a set of circles, the bigger ones will obviously have a longer perimeter. That means that any speed going along that perimeter needs to be transferred through some form of 1 : 1 gear ratio, or you can abuse the relation between speed and distance to artificially create one in exchange for the other.
It’s such an elegant depiction of the inverse relationship. As one term in the equation gets smaller, the other increases to conserve the total amount of energy.
@@MrClubjub haha sorry MrClubjub. He was my professor at WVU before he moved to Texas! Let’s go Mountaineers! Did he still play the fiddle while riding the Unicycle when he taught your class?
My physics teacher demonstrated this by spinning on a spinny chair with his arms out holding weights, then pulling his arms in. Safe to say he was a little dizzy afterwards.
This phenomenon is the simplest one in physics which I've never been able to intuitively understand, which makes it fascinating for me. Physically it makes perfect sense, yet it's not something I would ever come up with by myself, I don't think. Another one of those, albeit a little bit more complex, is the temperature of the air you blow out being dependant on how wide you open your mouth, not how strong you blow. I'll never forget learning that in a high school physics class, having not noticed it an any earlier point in my life. Turns out I'd been mistaking the change in the speed of the air for the cause, whereas it had also been an effect. I was amazed and couldn't stop testing it afterwards. I'd been wrong about something seemingly so natural for so long! I remember sharing this newfound knowledge with a friend, he seemed unphased about it though, "of course that's how it works" he said, more or less. Before that day, I would have said the same thing about my explanation. Goes to show how much you can miss by never investigating the "obvious" :)
For anyone wondering why it works , it is analogous to a situation in which we put a linear momentum to a rest object now suppose if its mass is reduced then it will speed up because its inertia is getting lower similarly in rotational dynamics the inertia does depnds on radius also other than its mass so if somehow we reduces its radius then its inertia decreases which results in increase in angular velocity.
thanks to this, it's speculated that black holes actually have donut-shaped singularities because all the rotation gets compressed into the smallest possible space, resulting in insane rotation speeds that stretch and reshape the singularity into a donut that is rotating ridiculously fast.
“donut shaped” is a stretch. They _are_ theorized to be rings, but since a ring with dimensions of 0,0,0 and a point with dimensions of 0,0,0 are indistinguishable from each other in every perceivable and measurable way except for the ring’s ability to spin.
Quick explanation for those who didnt understand: (1st ball) since I=mr2 thus if we increase the radius, moment of inertia increases. Which means moment of inertia decreases the ball's abilty to produce angular rotation. This causes a decrease in angular acceleration and thus angular velocity. (2nd ball) since I=mr2 and the radius decreased, which also decreases moment of inertia. By which the body's abilty to produce angular rotation increases. Which causes an increase in angular acceleration and thus angular velocity. Hope this helps!
it is called the law of conservation of angular momentum. The formula for the moment of inertia for such a sphere is the product of mass x mass distribution( here the radius of the sphere ^2) times some factor( like 2/5 for a solid sphere). The angular momentum of a rotating object = the moment of inertia (denoted by I) times the angular speed. (so I x w; where w is angular speed). when the sphere contracts, the mass is still the same, but the radius decreases, hence the I decreases according to I = mass x radius^2). But since there was no external force(or rather, torque) applied, angular momentum is conserved, meaning : (I x w) final = (I x w) initial. Since I decrease in the second case, w must increase to keep equality maintained. and that is why it spins faster when contracted.
This is why pretty much every black hole has spin, as well as a ringularity inside the inner event horizon (one where u will remain forever spinning at the speed of light when inside it) - if u compress matter down to an infinitely small point in space, that point will have “infinite” spin associated with it due to the conservation of angular momentum
I know that fact for ages. Still, it was sooooo satisfying to see that presentation. And the smile on professor's face when physics worked as usual. Love science. NEver lets you down.
As someone stated previously, neutron stars and white dwarfs, angular speed increases. So do black holes. In fact, there is a point that a black hole, if the moment of inertia in expanded is great enough and it contracts, it could form a naked singularity. Though no stellar body, in natural cosmos, has that type of expanded inertia.
The momentum kinetic energy was well conserved in that big but low speed thingy, and when it becomes small it has to speed up because there wasn't any energy loss of that momentum
I wish we all had such teachers .If in our college and school we were having such teachers so we would never be upset with physics learning 😊Yeah now we feel it burden super burden because we donot even understand😢
Law demonstrated, conservation of angular momentum. Now, Angular momentum (L)= Iw (I= moment of inertia, w= angular velocity) and I= (integral of two variables )MR² ( M= mass of the object, R= radius) now since Iw is conserved, (Iw) initial= (Iw) final. And since, R is reduced(also M distributed uniformly), I also decrease, but M is constant. As a result, w increases in the final result.
I remember this demonstration in class but not this cool, our teacher just stood on a lab stool grabbed the ceiling and spun around before tucking his arms in and out. Miss that guy hope he's still teaching there.
That smile at the end is called... Passion
Is he beta for showing emotions?
@@smartwater598hell no
@@smartwater598 no, it's nice to see people teaching something they truly care about
@@smartwater598, man’s a gigachad for teaching cool shit
@@judgment5090 100%
This is how figure skaters spin, they tuck arms in for fast multi spins, and reach out for graceful, slow spins
Yes... now that I think about it .
@@flishry You are joking right?
@@flishry Are you joking?
@@an9l1c1sm6 I don't think he's joking
@@flishry I'd trust a person who has studied this as their specialty to be honest, aka the man in the video.
This is how neutron stars get their astonishing rotation speeds, some of them rotate at like 42000 rpm
That's ridiculous, imagine the power of the magnetic field and current that would induce
@Ρгοηαtoг тεηdoη yup, they radiate pretty hard, slowing the speed dramatically over thousands of years. Later then they keep rotating at a slower pace much more peacefully
42000 rpm? Holy vtech
what object in the universe has highest rpm? blackhole?
@Darui blackholes don't have rpm per se, but they have an angular momentum measured as a fraction of the speed of light from 0 to 1. This momentum does not correspond to an actual rotation because BH is not an object but rather a region of space-time, which twists quite oddly and counterintuitively under the influence of rotational energy
This was my college physics professor! Dr Boyd Edwards!! Guy was a legend and was a perfect example of a good, passionate professor
Mine too, go Aggies!
what school?
Thanks for sharing the professor's name
Which college do you study bro
@@rgmoses2189UC Davis
If only physics in school I went to were taught in this passionate, sweet manner I wouldve paid much more attention. Great job, Dr. Edwards. We need many more teachers like you.
If only university physics was taught like this, I wouldn't have failed
Agreed 👍🏻
but what is the point of doing this? We can easily know what was gonna happen by doing very little math. What is the point of needing a whole example to know something which can be known in 3 lines
It would help, but only by a little bit. I assume
In our school we did this experment by a one sitting on a rotatable chair giving two weights to both hands. Telling him to keep tha weights closer and with a distant time to time while rotating. Consequently his rotating speed was increased and decreased
Short version of why this works: If you think about it, both configurations have the mass moving through the same amount of space in a second. It just so happens that when it's expanded that space covers fewer degrees of rotation as the same amount of space when it's contracted does.
I like thinking about things in these ways, thanks for the brain dope
so is this also explain why the earth looks like rotating slowly?
@@sugiyonotahu that has to do with relativity. It is hard to explain and I am not an expert
@@sugiyonotahu i assume it's just because it's really big
@@danzoom pretty much. The Earth at the equator has a surface velocity of ~460 meters per second. When experiencing this rotation on the surface, we don't feel like we are moving because we match the earth's surface velocity. TLDR: Earth's surface moves about 1000 miles per hour, we don't feel it because we are attached to it by gravity.
we need teachers like this
To anyone who wants to know the math behind this:
Angular momentum dictates that a spinning object's linear velocity should remain the same even if you change its radius.
According to the equation w=V/R (w being angular velocity, V is linear velocity and R is radius), as V remains constant, the larger the radius, the lower the angular velocity.
Thanks for the equation!
@@priyadarshinibvk you're welcome :)
Thankyou,nice guy
I would enter in his class even though I am not one of his student because he deserved this kind of praise😆😆 kudos to this beloved teacher🤗🤗
If you’d like to witness inertia in all its glory, go to a state government office
No need, I've visited a glacier before....
😂😂😂😂😂
I sure hope it keeps going
Nah. That's rather plate tectonics.
"Excuse me, where is the two hour parking for the library?"
"Is this some kind of joke?"
"Uh..?"
"You're under arrest."
Beautiful demonstration!
It's amazing how much u learn when ur not forced to learn things.
IW= constant so that W= constant/I , it means if I will decrease then W will increase. W= angular velocity , I= Inertia, BTW good example
Hey, thanks! Made me understand how it worked!
Is the constant=angular momentum?
@@iq_pi7211yes
The. l . W = constant
Then increase I ,decrease W.
Decrease I, increase W.
Result constant angular moment
@@iq_pi7211 yup
"Inertia is a property of matter" - Bill Nye Intro
Moment of inertia is a property of rotating matter
Bill Nye the say whatever we pay him to guy
Inertia and moment of Inertia are different things.
Lol he was so pleased it worked 😂👍
this guy was my physics professor in university.
Prove it nerd
@@georgeherbertmoonwalkerbush it is your burden to prove him wrong as the accuser
@@elijazfrazelsassafraz3100 no the burden of proof is on OP as he claimed a thing without proof.
@@James-ek3il no, burden is on nobody because this is the internet and he probably forgot he even commented about this
@@sombrerocat2971 no, the burden is on those who gave enough damn about any of these comment to make thier own instead of spending the same hour by doing something productive , that applies to me too :D
I love how satisfied he looks with that smile
THIS WAS MY PHYSICS PROFESSOR FROM UTAH STATE UNIVERSITY! Love this guy!
Seems like a knowledgeable and dedicated person! Nice!
👌
goddam, you're a lucky student. i went to a v v v good state school, but state schools are generally huge and due to their state funding, they tend to have more research competent profs than profs that can teach. in my 5 yr prog (at my school biotechnology and molecular biology was recommended to be finished in 5 yrs due to having 85% of our classes be lab work) we learned all of our maths (up to calc2), physics 101/102 and inorganic chemistry 101/102 by ourselves with the aid of the tutoring center. cz our maths and physics profs were on proof grants and our chem dept was on lunch cancer and stem cell research specifically and they were all trying to show results.
if this dood was my physics prof I'd prolly double major in physics too.
not gna lie, physical chemistry was the most difficult theoretical course I'd ever taken in undergrad.
You can feel this when you spin in an office chair. If you tuck your legs in you spin faster than if you stuck them out.
Hence Angular Momentum is conserved, as no external force is applied.
Isn't it Torque
Nice one short but best explaination
@@name4852 torque is done by a force but yes if you want to be precise it is torque
@@googloocraft1217 But torque can still exist even though Fnet = 0
I want a teacher like this one
Good teachers who are passionate about what they teach are few and far between
This is also a little engineering trick to keep in mind, since this applies to gears and levers and the entire reason concepts like torque even exist.
When you draw a set of circles, the bigger ones will obviously have a longer perimeter. That means that any speed going along that perimeter needs to be transferred through some form of 1 : 1 gear ratio, or you can abuse the relation between speed and distance to artificially create one in exchange for the other.
You can tell how proud he is of his example from the smile at the end, and he should be, this is a great demonstration
That’s a great explanation of conservation of angular momentum.
I literally had this exact experiment a few weeks ago in my first semester of my physic bachelor
That's actually a really cool demonstration of that effect, something even children could understand easily.
He is proudly follow his passion 🔥🔥💯💯
This comment section genuinely makes me happy. People actually commenting science instead of just "oh I still can't understand, I'm so cool bs"
Classic demonstrasion of conservation of angular momentum
It's awesome to see practically what we study in our books
Super cool demonstration. It definitely makes Moment of Inertia and Angular Momentum intuitive.
It’s such an elegant depiction of the inverse relationship. As one term in the equation gets smaller, the other increases to conserve the total amount of energy.
My physics professor back in college. Last day of school he rides on a unicycle while playing the fiddle.
Mine too! Go Aggies!
@@MrClubjub haha sorry MrClubjub. He was my professor at WVU before he moved to Texas! Let’s go Mountaineers!
Did he still play the fiddle while riding the Unicycle when he taught your class?
@@aneesrahil736 ya he did. Wrong Aggies tho. I meant Utah State University
Beautiful demonstration
My physics teacher demonstrated this by spinning on a spinny chair with his arms out holding weights, then pulling his arms in. Safe to say he was a little dizzy afterwards.
my teacher also did the same :)
Maybe this is what's happening with the universe expanding 😋
Universe doesn't really care about our current understanding of Physics. But, maybe.
@@the_science_fact The universe is what taught us about conservation of angular momentum and enforces it every time we test it (so far).
Like a gear or pully changing sizes . Cool!
I discovered this years ago as a kid by spinning like a top and then pulling in my arms and suddenly going light speed.
This phenomenon is the simplest one in physics which I've never been able to intuitively understand, which makes it fascinating for me. Physically it makes perfect sense, yet it's not something I would ever come up with by myself, I don't think. Another one of those, albeit a little bit more complex, is the temperature of the air you blow out being dependant on how wide you open your mouth, not how strong you blow. I'll never forget learning that in a high school physics class, having not noticed it an any earlier point in my life. Turns out I'd been mistaking the change in the speed of the air for the cause, whereas it had also been an effect. I was amazed and couldn't stop testing it afterwards. I'd been wrong about something seemingly so natural for so long! I remember sharing this newfound knowledge with a friend, he seemed unphased about it though, "of course that's how it works" he said, more or less. Before that day, I would have said the same thing about my explanation. Goes to show how much you can miss by never investigating the "obvious" :)
Already understood this, but it's so cool to see it in motion.
Best explanation of conservation of angular momentum I have ever seen..
For anyone wondering why it works , it is analogous to a situation in which we put a linear momentum to a rest object now suppose if its mass is reduced then it will speed up because its inertia is getting lower similarly in rotational dynamics the inertia does depnds on radius also other than its mass so if somehow we reduces its radius then its inertia decreases which results in increase in angular velocity.
this is why you spin faster on a swing if you put your legs in. physics is amazing
To be high on physics class, is just amazing
That was satisfying af when it expanded.
God I love physics-
thanks to this, it's speculated that black holes actually have donut-shaped singularities because all the rotation gets compressed into the smallest possible space, resulting in insane rotation speeds that stretch and reshape the singularity into a donut that is rotating ridiculously fast.
“donut shaped” is a stretch. They _are_ theorized to be rings, but since a ring with dimensions of 0,0,0 and a point with dimensions of 0,0,0 are indistinguishable from each other in every perceivable and measurable way except for the ring’s ability to spin.
Quick explanation for those who didnt understand:
(1st ball)
since I=mr2
thus if we increase the radius, moment of inertia increases. Which means moment of inertia decreases the ball's abilty to produce angular rotation.
This causes a decrease in angular acceleration and thus angular velocity.
(2nd ball)
since I=mr2
and the radius decreased, which also decreases moment of inertia. By which the body's abilty to produce angular rotation increases.
Which causes an increase in angular acceleration and thus angular velocity.
Hope this helps!
One of the reasons why I am passionate for science. So many cool things
And that's why a pull slash gives you more impact than a push slash.
If you're a physics lover , i know you smiled knowing what he is about to do, even before he explains
it is called the law of conservation of angular momentum. The formula for the moment of inertia for such a sphere is the product of mass x mass distribution( here the radius of the sphere ^2) times some factor( like 2/5 for a solid sphere). The angular momentum of a rotating object = the moment of inertia (denoted by I) times the angular speed. (so I x w; where w is angular speed). when the sphere contracts, the mass is still the same, but the radius decreases, hence the I decreases according to I = mass x radius^2). But since there was no external force(or rather, torque) applied, angular momentum is conserved, meaning : (I x w) final = (I x w) initial. Since I decrease in the second case, w must increase to keep equality maintained. and that is why it spins faster when contracted.
Perfect preparation to express moment of inertia.
Thats the spark students need in the classroom.
Making this damn thing with clips is also an another dedication
The same thing happens with black holes when they shrink because of Hawking Radiation . They spin faster and faster spewing more energy
Thats smile at the end, ive seen it its call passion for what you do.
People with passion are the Salt of this earth.
And this is how we theorize that black holes have a ringularity instead of a singularity
This is why pretty much every black hole has spin, as well as a ringularity inside the inner event horizon (one where u will remain forever spinning at the speed of light when inside it) - if u compress matter down to an infinitely small point in space, that point will have “infinite” spin associated with it due to the conservation of angular momentum
I've always known this but I love simple examples like this
Well that was certainly a visual treat
I know that fact for ages. Still, it was sooooo satisfying to see that presentation. And the smile on professor's face when physics worked as usual. Love science. NEver lets you down.
Its like on a playground with the spinny things and when you tuck yourself in you just get transported to the 4th dimension
Genius, that is how teachers must work.
As someone stated previously, neutron stars and white dwarfs, angular speed increases. So do black holes. In fact, there is a point that a black hole, if the moment of inertia in expanded is great enough and it contracts, it could form a naked singularity. Though no stellar body, in natural cosmos, has that type of expanded inertia.
I used to do that when spinning on a chair and stretching/flexing my legs horizontaly.
Wow, love this demonstration.
Thats also why neutron star and black holes spin thousands sometimes millions per minute. They shrunk in diameter but conserved their angular momentum
I love it when “physics teachers” quit pretending for a second and just start performing magic
You can do this in a kids play park.
On the roundabout crawl to the centre.
Other revolving kit can do it, too!
This is way more fun with two dumbells, an office chair and a reckless friend
A Great way to demonstrate the conservation of Angular Momentum!
I've seen dancers do this while spinning on their head and it LITERALLY looks like magic!
physics is so crazy and amazing
The momentum kinetic energy was well conserved in that big but low speed thingy, and when it becomes small it has to speed up because there wasn't any energy loss of that momentum
Much like momentum, angular momentum is also conserved. As you decrease the moment of inertia, angular velocity increases to conserve angular momentum
I'm glad he did it first with no spinning cause one might think it was the energy of the pull that acelerated the object. It really look like so.
Me sitting on the rotating chair and opening and closing my arms everytime !! 😂
I wish we all had such teachers .If in our college and school we were having such teachers so we would never be upset with physics learning 😊Yeah now we feel it burden super burden because we donot even understand😢
This is just beautiful
"Listening to something you don't like is called stress observing something you like is called passion! "
- one of the greatest influencer
Law demonstrated, conservation of angular momentum. Now, Angular momentum (L)= Iw (I= moment of inertia, w= angular velocity) and I= (integral of two variables )MR² ( M= mass of the object, R= radius) now since Iw is conserved, (Iw) initial= (Iw) final. And since, R is reduced(also M distributed uniformly), I also decrease, but M is constant. As a result, w increases in the final result.
So what I've learned is that high moment of inertia--> greater resistance to movement-->
Angular momentum is low
I knew that would happen but what makes happy is how fast it speeds up.
I always love in physics but this is so AWESOME, Thank you so much!!!
Very cool display.
I need one of those collapsing balls. I remember being small enough to fit in one of them fully expanded back in like 2000. I was about 4!
They're a classic toy. I wonder if they're still being made?
The fact I'm literally doing this in physics rn makes me feel these shorts are reading my mind.
This same concept is behind the unbelievable rotational speed of neutron stars who have angular velocity nearly 712 rotations percsecond
This reminds me of those spinning things at the play parks
I’ve learned this when I was 6 when I was playing on a office chair spinning myself around when I’m waiting for my dad to finish his conversation
Good example and illustration of conservation of angular momentum.
He got chills at end
I love how I know this just from spinning around my room
Damn I love physics.
That was really interesting :)
I remember this demonstration in class but not this cool, our teacher just stood on a lab stool grabbed the ceiling and spun around before tucking his arms in and out. Miss that guy hope he's still teaching there.
I only liked because of how proud he was at the end
Now we just need to figure out how to apply this to spaceships.