IIT JEE , AIEEE Forum - Physics , Mechanics

Ksudha_iit

this is for all those who admire rotational dynamics...

here it is ....

1) we can use instantaneous point of rest for writing the torque equation only when the body is symmetrical and it should be on ground....for fast results

it can be used for non symmetrical bodies also i e when the ipr (instantaneous point of rest) is not in the same vertical line of the centre of mass...
but be careful of writing the torque of pseudo force...

for those who do not know this method earlier...we can use ipr for writing the torque equation because the pseudo force's torque will lie in the same vertical line so it wouldnt produce any torque as such ....

2) during a rod and a mass collision...most favourite questions of iit
conserve angular momentum about the point of collision...

the most amazing part of this solution is that whatever the collision might be ...elastic inelastic or semi....where it is quite complicated in getting the relation betn v and omega....it comes directly....using this and the only thing that will vary is the distance of point of collision..the same relation comes if the distance of point of collision is same and different ....collisions are taking place

3) and choose always a point which is not accelrated ( so as to avoid further errors...like writing pseudo force's torque ) so that atleast we get...relieved of unwanted ...forces ...that more and more equations ...to solve..

4) beware guys ....torque = i alpha can be written only using two points ..one is cm...and the other where it is hinged....

i gave the explanation why we use ipr in some cases above...

hope this helps guys...

go on iit is awating ....!!!

Ask & Discuss Questions with Community & Experts