When the bodies are attached, by conservation of anular momentum we can calcuate its final omega which comes out to be MW/(M+2m). Now you can calcuate the difference of initial and final rotational KEs of the system. Ans will be option (4).
@yashpandey95508 жыл бұрын
when the smaller block is dropped then , the friction and the normal reaction b/w the block and the disc are internal forces , so we will not account them while calculating torque but the force mg on the block is not an internal force and its torque mgr must be accounted for , which will result in angular momentum not being conserved , which is not happening here , why ????
@physicsgalaxyworld8 жыл бұрын
+Yash Pandey Think carefully... torque due to mg (mgr) is acting in horizontal direction not along the rotation of body.... it is balanced by the force applied by axis of rotation on thickness of the disc which is keeping the disc horizontal...
@yashpandey95508 жыл бұрын
Ooh , so only those torques which are along the AOR (and if making some angle with AOR then their component along AOR) is taken while solving problem....Ya i got it that the torque is along the disc but can you please tell me , the reason why the torques which are along the bpdy aren't able tp contribute to its rotation , as i didnt find any videos with that sort of thing being discussed ! Thanks :D
@yashpandey95508 жыл бұрын
*bpdy = body ; *tp= to
@physicsgalaxyworld8 жыл бұрын
+Yash Pandey As in given cases AOR is fixed about which only the body can rotate so only those torques are considered of which vector is along the axis rest of the torques are balanced by the opposite torque by AOR so not considered in any cases and we ignore these but you must remain careful for such cases as questions can be asked on these as well...
@yashpandey95508 жыл бұрын
But if the torque makes an angle alpha with the AOR then we will take its component along the AOR AND NEGLECT THE component perpendicular to the AOR ??
@amankapoor76655 жыл бұрын
how to decide which force is internal and which one is external?
@jigyasa1093 Жыл бұрын
sir the mg will not change the rotation but it will tilt the disc right?
@tejakoncha18163 жыл бұрын
Sir what u telling is enough for jee
@tpsicmin3 жыл бұрын
Thank You Sir😎
@samikolarkar72272 жыл бұрын
Sir why angular momentum act on any body while rotating?
@jigyasa1093 Жыл бұрын
sir have you covered the topic of hinge forces?
@repudirajasekhar38846 жыл бұрын
Thank u sir
@prabhatkumarverma2007 жыл бұрын
sir....while balancing the angular momentum about any axis.... should we take into consideration only those angular momentum which are along axis of rotation ????
@jatinbhatt78266 жыл бұрын
Sir since angular momentum is a vector quantity. If its direction is changing with time and not the magnitude then can we say there must be torque ??
@physicsgalaxyworld6 жыл бұрын
Yes. Thats correct...
@jatinbhatt78266 жыл бұрын
Physics Galaxy thanks sir
@namaste6313 Жыл бұрын
@@jatinbhatt7826 Kb kaha par ho
@jatinbhatt7826 Жыл бұрын
@@namaste6313 ??
@namaste6313 Жыл бұрын
@@jatinbhatt7826 ab konsa college me ho??
@CristianoRONALDO-nw8hr4 жыл бұрын
Centrifugal force will not act on dropping the block on the moving disc???
@next_thing_to_god7 ай бұрын
friction will balance it
@sumanyugarg45769 жыл бұрын
sir ..i got a little bit confused..why we havent taken the mg(mass of the small block placed)..?i reach to an explanation that the normal forces and frictional forces are internal..Mg(weight of bigger block) is through centre and also the hinge forces through the centre..(due to these torque become zero..) then..mg is left..and no other force to cancel its torque..?
@physicsgalaxyworld9 жыл бұрын
On block mg and N are the only forces acting in vertical direction so these will get cancelled out... Only force left on disc will be N, the normal reaction in vertical direction which will extert a torque but it will not be affecting the rotational motion of disc so we are not using it.... Torque due to this N will tend to tilt the disc which is balanced by a couple exerted at center by hinge...
@himanshuacharya2152 жыл бұрын
Thanks sir from the bottom of my heart 🙏🙏sita ram
@Ashutosh._.Gupta_6 жыл бұрын
Why friction acts in both directions?
@physicsgalaxyworld6 жыл бұрын
Every force acts in pairs... one is action and other is opposite reaction... but the two forces always act on different bodies... here also the two friction is acting on different bodies...
@sparshagarwal34947 жыл бұрын
Sir is newton's third law also has something to do with torque
@physicsgalaxyworld7 жыл бұрын
Not directly... its for force only...
@sparshagarwal34947 жыл бұрын
Physics Galaxy A, coil of radius R carries current I. Another concentric coil of radius r (r
@physicsgalaxyworld7 жыл бұрын
Here energy is conserved... and simply by conservation of energy above que can be solved... there is no such law for conservation of force or torque...
@himanshumarmat38588 жыл бұрын
Respected Sir if we change the definition of our system, we simply changes the external or internal force/torque but practically the situation is same so, will the linear/angular momentum still be conserved if not that why ?
@physicsgalaxyworld8 жыл бұрын
Didn't get you... what exactly you want to ask... pl clarify... in any case if external force is acting on a system, its reaction is outside the system and due to net non zero force conservation laws cannot be applied, similar state is true for torque also...
@himanshumarmat38588 жыл бұрын
+Physics Galaxy Sir, consider two blocks lying on a friction less surface moving towards each other we consider both the blocks as our system, they collide then momentum is conserved as no external force is there. But now we consider one of the box as our system and the other box collides with it now the situation is practically same but in this case according to definition of our system there is external force, the momentum should be conserved practically but not theoretically . Please help.
@physicsgalaxyworld8 жыл бұрын
As this query is not linked with this video, it may distract viewers of this video so I suggest you to post any other query in INTERACT tab of our website www.physicsgalaxy.com under the topic of your query, that will not only get other people in discussion but thats a forum where we can discuss on any topic....
@Prodbybah3 жыл бұрын
@@himanshumarmat3858 bhai where are you now
@HarishKumar-yr9gv Жыл бұрын
@@himanshumarmat3858 bro even practicaly in the second system momentum will not be conserved
@indusaini15235 жыл бұрын
Sir is it due to the fact that mg to produce torque should have a axis perpendicular to the given axis..
@smittavate57903 жыл бұрын
i have the same doubt....please elaborate what you understood
@vanshmishra71197 жыл бұрын
sir but the gravity is acting on the whole body right? even if disc and block is the system then i understand ki AOR will cancel the effect fo force but not torque then Why did you conserve? pls sir do Answer half of my posted questions are not answered tho i follow all your vid.s almost and you ans the foolish comments those calling the accent bad an all ...and not my doubts i humbly ask you to clear my doubts thnx.....................in short if you have taken the disc block system then what force is cancelling the torque by gravity?
@mehulsoni35816 жыл бұрын
Sir suppose that we have a hemispherical bowl and a ball is projected along the rim of the bowl with velocity u and after some time its velocity (say v) makes an angle theeta with the horizontal tangent of the bowl. Can we write vxcosine(theeta) = u ?
@physicsgalaxyworld6 жыл бұрын
No... use conservation of angular momentum to calculate it...
@mehulsoni35816 жыл бұрын
Physics Galaxy Sir but why horizontal speed won't be constant
@physicsgalaxyworld6 жыл бұрын
because radius of path is decreasing and the normal reaction on ball is exerting a horizontal force on it...
@mehulsoni35816 жыл бұрын
Physics Galaxy Sir the horizontal force will be radial while the horizontal speed will be tangential. Then how can the force decrease the speed ?
@adityarawat49643 жыл бұрын
It will case like banking of roads
@abhisheksahu67257 жыл бұрын
sir if external torque is acting but it's resultant torque is zero Will the angular momentum will remain conserve?
@physicsgalaxyworld7 жыл бұрын
Yes... but only about the point for which net torque is zero...
@repudirajasekhar38846 жыл бұрын
Sir... once plz explain how torque is zero...
@physicsgalaxyworld6 жыл бұрын
Supporting external force on system is acting on the axis of rotation only where the platform is hinged... so torque of this force about this axis will be zero...
@darkflamev11 жыл бұрын
Thank you so much! :)
@hermionegranger88333 жыл бұрын
Where are you these days?
@GopalSharma-nj2zk3 жыл бұрын
hi uncle
@sohruti3 жыл бұрын
@@hermionegranger8833 omg 😂
@edunitianmanab28363 жыл бұрын
@@hermionegranger8833 If you are so clever, you do this
@indusaini15235 жыл бұрын
Sir is this disc is not hinged at centre...??? Plz help sir..
@physicsgalaxyworld5 жыл бұрын
Yes it is hinged...
@sandeepgarapati79659 жыл бұрын
sir,in the below question they are given 2 masses so then final angular velocity is MW/(M+4m).....is it right or wrong..sir..if then ans is changed
@hermionegranger88333 жыл бұрын
Where are you these days?
@edunitianmanab28363 жыл бұрын
@@hermionegranger8833 In other words, Did you make it to IIT
@next_thing_to_god7 ай бұрын
@@hermionegranger8833 why emma watson pfp
@next_thing_to_god7 ай бұрын
@@edunitianmanab2836 did u tho?? (just asking )
@hermionegranger88337 ай бұрын
@@edunitianmanab2836 yeah I did
@ashu13145 жыл бұрын
Sir why friction is acting in 2 directions
@HarishKumar-yr9gv Жыл бұрын
One is exerted by mass m and other from disc
@darkflamev11 жыл бұрын
Could you help me out with this? A ring of mass M and radius R is rotating about its axis with angular velocity W. Two identical bodies each of mass m are now attached gently at the two ends of a diameter of the ring. What will be the loss in KE due to this? Options are: 1) ((M+m)M(W)^2(R)^2)/(M+2m) 2) (Mm(W^)2(R)^2)/(M+m) 3) (m(M+2m)(W)^2(R)^2)/M 4) (Mm(W)^2(R)^2)/(M+2m)
@halamadrid13uclbarcelonado663 жыл бұрын
I will help u
@awesomeguy61712 жыл бұрын
@@halamadrid13uclbarcelonado66 Kaafi Jaldi aa gaye help karne
@halamadrid13uclbarcelonado662 жыл бұрын
@@awesomeguy6171 😂🤣😂🤣8yrs ago lol
@alexs62846 жыл бұрын
really very helpfull :):)
@adityapathak5186 жыл бұрын
Sir please help me ye chapter thoda samaj a rha hn sir Kain book solve kare jisase strong ho jye
@physicsgalaxyworld6 жыл бұрын
you can use our 'Physics Galaxy' series of books...
@adityapathak5186 жыл бұрын
Physics Galaxy Thanks a lot sir
@varunrajesh17293 жыл бұрын
@@lifestough2546 chup
@physicsfaadoooo54736 жыл бұрын
Respected sir, In the example you told that there is no Torque due to ext firce about the com. How and why?
@physicsgalaxyworld6 жыл бұрын
because line of action of force passes through COM so about COM torque of this force will be zero... as torque is the product of distance of line of action from the point...
@YogeshSharma-ys3hm6 жыл бұрын
@@physicsgalaxyworld sir here please specify which force are you talking about and how acis of rotation can apply any type of force on the body please correcct me
@physicsgalaxyworld6 жыл бұрын
If the AOR is passing through COM then due to rotation of body COM remain at rest but if this is not the case then COM will revolve in a circular path which is possible only if body experiences an external force along radially inward direciton... this is the force AOR applies in such cases...
@tanishjeetsingh43506 жыл бұрын
what exactly is this external torque
@divitgoyal59016 жыл бұрын
sir is instantaneous AOR not in jee mains syllabus ??
@physicsgalaxyworld6 жыл бұрын
No.
@physicsgalaxyworld6 жыл бұрын
Only in case of pure rolling of a body on a surface you can use this concept of IAOR to quickly solve MCQs.
@surajkumarbehera6 жыл бұрын
Physics Galaxy sir what is instantaneous AOR??
@vishalgupta8957 жыл бұрын
When I first watch the video I never understand but watching after a few days I understand all the concept why is it happen to me sir
@harrykane13476 жыл бұрын
happens to everybody
@hermionegranger88333 жыл бұрын
Yes, it happens with everyone...where are you guys these days?