Wheel Conservation of Angular Momentum Demonstration and Solution

[@zingwatt9929]

Thank you so much! I remember doing this in my physics lecture but how you explain it makes so much more sense to me now. Thank you so much

[@arimirsky2769]

Thank you, this really helped

[@FlippingPhysics]

You are welcome!

[@Rica-In-Love]

You have the smartest students, bravo :-)

[@anthonytafoya3451]

Great video my brother. You can expect many more visits from me in the future. Absolutely splendid lad!

[@pepepacheco6199]

Thank you. Excellent explanation...

[@drthraxine]

But why did it happen ? You didn't explain why, you just took the final result and solved the equation backwards

[@nasirkhalid6770]

Wow really mind blowing thank you very much you made my day.

[@FlippingPhysics]

Always great when I can make Nasir Khalid's day!

[@dtgiabao9915]

Much appreciate! This feels like magic to me. Thank you so much

[@jamil5522]

How did you exert torque by rotating the wheel? What is the force and radius?

[@motionhits]

Thank you for this.

[@CruxCourse]

Thankyou sir.... Enjoyed learning with you😊.......sir PLEASE make REVIEW videos for THERMODYNAMICS ,OPTICS and MODERN PHYSICS ...i would b very Thankful to you....Earlier even after studying everything I was having Lack of confidence ,,n thats bcoz im not having any idea about how to Revise Effectively.... BUT AFTER i found you on youtube Oneday.... I GOT IT ( how to review effectively)...... N this is all bcoz of ur dedication for physics..... I am preparing for an entrance n after watching ur video content my performance in weekly test has INCREASED A lot..... AGAIN THANKKYOU SOOOO MUCHH SIR🙏🙂

[@FlippingPhysics]

Someday I will certainly make videos for those topics, however, it will one a long time until that does occur. I am sorry I cannot be more helpful with those topics at this time. Glad I have been able to help you with your weekly tests!

[@flaviooliveira4219]

How good must the chair be (in terms of rotating frictionless) and/or how fast must the wheel spin in order to really see that?

[@FlippingPhysics]

How frictionless? Quite frictionless. How fast? Quite quickly. How massive? The more massive the better. How safe? Don't fall!!

[@flaviooliveira4219]

​@@FlippingPhysics Omg thank you for the quick answer! On monday I intend to do that with my students, but although I'm spining really fast the wheel, my chair doesn't spin at all. I'm using a regular office chair, and that might be the problem

[@FlippingPhysics]

@@flaviooliveira4219 Yeah, I borrowed a colleague's chair especially for this video because I did not have one which as frictionless enough. Best of luck!

[@samarthrao8051]

please start thermal physics and optics also . they are also extremely important

[@jjs9473]

Caution: External torques act on the person + stool system. The stool can only rotate freely around the axis perpendicular to the ground. I.e. the system person + stool can gain or lose angular momentum parallel to the ground. Thus the statement that the angular momentum is preserved is wrong. Only the component parallel to the axis of rotation of the stool is preserved. Proof: The moment you start rotating the wheel, the angular momentum of the wheel no longer points perpendicular to the ground, hence the system person + stool gained angular momentum parallel to the ground.

[@peacecop]

I just came to the same conclusion after many hours of watching videos, reading, and thinking. This video was the last piece missing from my puzzle. The arithmetic helped. And also other pieces. If there would be a vertical axis then the system would rotate both horizontally and vertically. How can I restore the initial angular momentum if it was directed at a right angle sideways and there was nothing to compensate it for? Now I see that the initial angular momentum was not crucial as only one axis was in the play.

[@fuglbird]

How to make a simple concept complicated. Demonstrations on the chair with with different initial orientations of the wheel spinning axis usually leads to a better understanding.

[@gurmansingh1878]

It really helps me. And wonderful explanation

[@FlippingPhysics]

You are welcome!

[@gurmansingh1878]

Flipping Physics sir I am from Punjab (India)

[@FlippingPhysics]

Great! I am from The United States. I think the physics is the same over there on the other side of the planet. 🙂

[@gurmansingh1878]

@@FlippingPhysics absolutely right sir. But i have a dream to visit america for higher studies and bright future..

[@broysthgaming3877]

But, some book said because, the rotating momentum of the wheel always move in to the direction of the torque that you apply on the wheel. And this make sense to me but, when I see another video I really confused Thus, could you explain to me please?

[@broysthgaming3877]

Reply to me quickly because, I need to understand that.

[@peacecop]

Yes, the torque and angular momentum have the same direction.

[@ericakash3756]

Wow thank u so much

[@athulasirimal394]

Wooooow.interesting to watch.nice

[@FlippingPhysics]

Thanks!

[@meghpatel8727]

Ya that was amazing had fun

[@learningisecstatic9348]

Sir it is assumed that no external force is applied to the whole system. So the total kinetic energy of the system should remain constant. The solution suggests that the MAGNITUDE of the angular velocity of the wheel is SAME as before. So its kinetic energy is unchanged. But the man and the stool gets anguler velocity. So they get kinetic energy. So kinetic energy of the system is not conserved. Though no external force is applied to the system. Where am I going wrong? Please help sir. Hope you are well.

[@FlippingPhysics]

Under what circumstances does the mechanical energy of a system remain constant?

[@learningisecstatic9348]

@@FlippingPhysics when no work is done by the force applied and no work is done by the friction.

[@FlippingPhysics]

@@learningisecstatic9348 Right. We are pretending there is no friction. (There is, unfortunately, and it is slowing everything down, but we are ignoring that.) Is there work done by a force applied? Yes. In order to bring the masses closer to the axis of rotation, I have to apply a force to the masses. Therefore, I am doing work on the masses, in the absence of friction, the amount of work I do on the masses (in this case the net work) equals the change in kinetic energy of the system (net work equals change in kinetic energy theorem), therefore the change in kinetic energy equals the work done by the force applied on the masses.

[@learningisecstatic9348]

@@FlippingPhysics so sir we can treat the force that is caused by the interaction of the masses in a system as force applied. I thought force applied must be caused by some external agent .

[@FlippingPhysics]

A force applied is just one object pushing or pulling on another object. Get on a merry-go-round and try to pull yourself in to the middle. It actually takes quite a bit of work. www.flippingphysics.com/merry-go-round-conservation.html

[@UnbiasedSports]

Would you be able to answer "why 1/3rd of the moons rotate opposite of the rotational directional of their planets. How is that possible if there is no angular momentum problem." Btw that was a question given to me :(

[@flighted2513]

Ok so basically you can sum it up Lpersoninitial+Lwheelinitial = Lpersonfinal+LwheelfinalLet's just say that the initial angular momentum of the wheel is Iw (pretend the w is an omega), which implies that the wheel is spinning in a counterclockwise direction. Now lets say the wheel is flipped 180 degrees. Now it will be spinning in a clockwise manner. So that means the new angular momentum is -Iw. the initial angular momentum of the person is 0. The equation is thus Iw = Lpersonfinal -Iw. So then move it and it is 2Iw, which implies that the person HAS to spin counterclockwise. This is a simplified take on it. Any greenspan kids comment

[@sweshine25]

Flighted great👏

[@BanValsimot]

This is mind boogling....by rotating the wheel you have reversed it's spin to CW direction. But in order to keep the original angular momentum of the system present -> wheel started turning you in the CCW direction. It is logical from experience by weird when you think about it....

[@maurcusr]

Thank you, this comment is the only way I understood after multiple videos explaining it.

[@ALoonwolf]

"As much as I wave my arms and legs around I cannot cause the system to rotate." Didn't try very hard did you? I tried for five seconds and immediately got a technique that worked. Instead of wildly waving your arms and legs around seperate your top half and bottom half into units that rotate.

[@FlippingPhysics]

Okay. What is your point?

[@peacecop]

Please show it in your own video.

[@MrTouge240]

"Hhhweeeeeelll"

[@TheAnimammal]

The rotation of the stool is due to the gyroscopic effect and this demonstration has nothing to do with conservation of angular momentum. If you measure the results, you will confirm that angular momentum is not conserved. Good physics should be backed up with empirical evidence - not demonstration.

[@shailkumarjain]

Could you please explain it further ? and how angular momentum is not conserved ? Thank you..

[@carultch]

@@shailkumarjain This is a video that discredits John's talking points. kzbin.info/www/bejne/j3iskKaNf5aBodE

[@jjs9473]

@@shailkumarjain John Mandlbaur is correct. Check one of my comments.

[@peacecop]

Is it because there is just one axis?

[@TheAnimammal]

@@peacecop If I understand your question properly, No. I made this discovery doing research and development and very quickly recognised very early in the process that balance was important because the prototype models destroyed themselves at any serious speeds. My later models which led me to this discovery used directly opposed weights which could spin freely without vibration.