Doubt from Rigid Body Dynamics

I am doing rotational mechanics questions first time (due to my health problem I can’t attend lectures) so they can be basic please help in this thread in completing this chapter

2nd ko thoda explain kar do koi nahi samjh aa raha

maan lo ki ek disc rotate kar rhi aur axis disc ke parpendicular hai …acc to ques A vector lies along Axis …
Ab agr kisi R distace par disc par koi partice hoga (suppose) to uspe centrifugal radially outward lagega…aur diac ke plane mein hi hoga …matlb jo.B vector hoga wo disc ke plane mein hoga…now since disc and axis are perpendicular hence agnce is 90° …and scalar product zero ©


I eagerly wants to know why the question mentions resultant force then @Abhinav.08

did’nt get your ques…please explain a bit

Bro , read the question it says resultant force

it might mean net resultant of centrifugal and tangential force uniform circular motion not mentioned still net force in plane of disk

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Yeah, didn’t thought that still the resultant will be in the same plane.


plz help with this

The vertical wall and the horizontal wall don’t let the lowest point of the hemisphere to move.
Therefore , the line passing through this point at the junction becomes IAOR.
Apply torque equation about this point.

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Ans is 3


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Time for silly doubt : Q 23

Where I am wrong if I solve by this diagram and not the other one

My reasoning : Because it can’t be rotated by it’s one edge

Bro in first diagram ur rotating the lamina about one corner…not an edge

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True man , totally forgot what is edge !!
Can I get " Chullu bhar pani"

Another basic one

10*pi/18 newton

Well ans is 0.87N
Solving your answer gives 1.744 just double of that

ok got it just sending