Dr Anderson You are the person who truely knows how to relate the mathematical dynamic to real world dynamics. yeaaaah
@johnholme783
4 жыл бұрын
Chrystal clear! Thank you.
@truemaker8590
6 жыл бұрын
You are greatly awoseme me and friends watch your videos on our doubts its really help us to take that
@ShoTime017
Жыл бұрын
ty!
@mohammedyaseen2504
4 жыл бұрын
Thanks 🙏
@yoprofmatt
4 жыл бұрын
Mohammed Yaseen, You're very welcome. Glad you're enjoying the videos. You might also like my new site: www.universityphysics.education Cheers, Dr. A
@ptyptypty3
7 жыл бұрын
Excellent Video, Dr. Matt.. :) thank you..... all your videos are so CLEAR and Internalizeable. (is that a word?) .... I do have to ask you a question along the same line as this example.. I saw in another book that if you have a TOY TRAIN set.. and the train travels around in a Circle.. AND. if you have this switch track that switches the train from the outside track to an INNER circular track.... then the speed of the train does NOT... i repeat NOT.. speed up as the train diverts to the Inner circular Track.... Now that seems to Contradict the Conservation of Angular Momentum.... Can you visualize that problem?... can you explain why the Train does NOT speed up as it diverts from the outer track to the inner track?... Thank you for your response... it is an interesting problem.... If you need a reference to the Book I referred to then just ask... it was a Physics book called THINKING PHYSICS by Lewis Carroll EPSTEIN..
@yoprofmatt
7 жыл бұрын
Very interesting point Philip. I love the comment about the train moving to a different circular track and not changing speeds. It seems like this should violate conservation of angular momentum, but of course it does not. I'll try to make a video explaining why this might be, but here's my thinking: Say the train goes from a radius R track to a radius R/2 track. Initial angular momentum is MVR and final is MVR/2 (which of course do not equal). So where does the extra angular momentum go? It goes into the Earth! For the train to go from the outer radius to the inner radius, there has to be a force applied to the train which will have components both radial AND tangential to the circle. This tangential force from the track also pushes back on the Earth. And if there is a force and a radius there is a torque which causes the Earth to pick up the extra angular momentum. How much angular momentum does the Earth pick up? Exactly MVR/2 so conservation of angular momentum holds. I worked this out with a drawing of the "extreme" case where the track makes a 90 degree turn, then another 90 degree turn to get on the inner track. I'll try to share this in the video. Cheers, Dr. A
@ptyptypty3
7 жыл бұрын
wow, EXCELLENT concept Matt... thank you... I'll be reReading your description a couple of times to Visualize it.... Thank you for responding and for responding in Depth... I truly appreciate it... I'm not your typical "student" . lol, I'm 62 years old and now I have time to Relearn Physics and Calculus, all in an effort to learn about the things I took for granted, the Laws of Nature!! :) .. Thank you Again.. Your style of teaching and your unique Presentation are truly effective and even entertaining.. Peace always....
@ptyptypty3
7 жыл бұрын
by the way, I tried to find a VIDEO online that demonstrated the Toy Train switching to an inner track, but NO LUCK.... then I thought about using a marble to run along an outer track and then the marble switches to an inner track.. but, decided not to construct it.... ANYWAY.. again.. thanks Dr Matt for your consideration and efforts at trying the Extreme cases.. I look forward to your Video as presented in your typical COPYRIGHTED and PATENTED style.. lol.. Thanks!!
@ptyptypty3
7 жыл бұрын
One last thought, sorry to HOG your comment section... in regards to the train switching from the Outside Track to the INNER Track.. and it's Speed remains the same.... and in consideration to your reasoning about the Earth receiving Half the Angular Momentum...... what happens if the Train is switched BACK onto the Outer Track?.. does the train keep the same Speed?.. does it Speed up?.. does it slow down? does the Earth give Back the Angular Momentum it received earlier?... Hard to believe that so many What Ifs and How does it work, etc all come into play... Gotta love physics!! :D ..
@yoprofmatt
7 жыл бұрын
Same speed. Takes the angular momentum back from the Earth. Cheers, Dr. A
@johnjordan3552
3 жыл бұрын
Is there a (mathematical) proof for the conversation of angular momentum?
@anhkhoa5689
4 жыл бұрын
I'm kind of confused. Are the velocities, in this case, are tangential velocities which equal to omega.R? Since we reduce the R, should the Velocity need to be slower ?
@yoprofmatt
4 жыл бұрын
Anh Khoa, Your first question: yes. Your second question: no. If L is constant, then mvr is constant. Reduce r, v must increase. Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A
@oneinabillion654
3 жыл бұрын
Hi, by making the string shorter don't we apply a force that transforms to centripetal force(external torque), so angular momentum not conserved? How should I think about this?
@carultch
2 жыл бұрын
Good question. Indeed we do apply a force, but by the problem setup, this force is aligned with the radius vector from the reference point to the object in motion, about which we calculate angular momentum. As a consequence of this, r cross F will equal zero, and there is no net torque. Likewise, r cross (m*v) is also a conserved quantity. There will be a change in linear momentum from this force, but not a change in angular momentum. If you are curious to see a numerical method calculation from first principles, reply with your email address and I can send you spreadsheet that shows what happens with an object with tangential velocity receives a constant magnitude force directed at the origin. It traces out a precessing ellipse, when the force is something other than 0 or m*v^2/r (the trivial cases). When you calculate the cross product at every point along the way, L=r cross (m*v), you get a conserved quantity. You can also see that linear momentum changes are accounted for by the impulse of this force, and that kinetic energy changes are accounted for by the work done by this force.
@JossinJax
5 жыл бұрын
Doesn't v already incorporate r? (v=wr). So L =mwr, right?
@yoprofmatt
5 жыл бұрын
For a particle on a string, if L=mvr and v=ωr, then L=mωr^2 Cheers, Dr. A
@pmahantakiit
7 жыл бұрын
If instead of changing the radius we change the mass as 2m what will happen to its velocity.
@docfawadahmed
7 жыл бұрын
Bro! Angular momentum is always conserved i.e constant. Any quantity change will affect the other quantities. For example, If you increase r the velocity will decrease to be constant. Similarly, increase mass will decrease velocity. Lets chek equation, L1=L2 I1w1 = I2w2 m1r1^2w1 = m2r2^2w2
@carultch
2 жыл бұрын
Since mass is conserved, we cannot simply change the mass, without taking in to consideration the existing conditions of the mass we add to it (which let's assume would start out as stationary). We can either synchronize the new mass so that it matches the position and velocity of the existing mass, in which case there would be no change in the velocity when joining them together. Or, we could have it collide with a stationary new mass inelastically, in which case, the two of them would slow down. Colliding with an initially stationary identical mass, means that the speed will be cut in half.
@dastanabilev
6 жыл бұрын
wait. Does he write from right to left (related to him) ?
@carultch
2 жыл бұрын
You can see that his wedding ring (traditionally on the left hand) is on what appears to be his right hand, and he is writing with the other hand. He uses a mirror between his board and the camera, so that the text on the video appears normal. The text appears normal from his point of view. Students who watch him in the flesh, will see backwards writing on their side of the board. They will see the video footage on an adjacent display, so the writing appears normal.
@engr.tonystark3504
Жыл бұрын
Isn't angular momentum = Moment of Inertia x angular velocity
@zwijac
3 жыл бұрын
In relation to the conservation of angular momentum: If the Big Bang Theory is true, and the universe began with the big bang.... Why do two planets spin backwards?
@ezra2370
2 жыл бұрын
Big Bang is not actually a bang
@carultch
2 жыл бұрын
@@ezra2370 True. "Big bang" was a term coined by its critics who proposed the steady state universe hypothesis instead. Its first proponent called it the hypothesis of the primordial atom.
@baurresearchcc23
8 жыл бұрын
Conservation of angular momentum does not apply to this scenario. As the radius reduces, the angular momentum also reduces. The angular velocity increases because the circumference is less and the ball has a smaller circumference to traverse. The magnitude of the rotational velocity remains constant.
Пікірлер: 29