# bend it like a rod?>>>>>>

A thin rod of length L and mass M is bent at its midpoint into two halves so that the angle between them is 90o. The moment of inertia of the bent rod about an axis passing through the bending point and perpendicular to the plane defined by the two halves of the rod is

ML2 / X
X is ?

(1) 6
(2) 12
(3) 18
(4) 24

1
Akand ·

who said tht???? if ther r 4 slices... and u take out 2 slices...is it still d same???? first u had a circle now u hav a semicircle.........

62
Lokesh Verma ·

anvay it is a thin rod.. neither solid nor hollow :D

1
Akand ·

dude anvay its 'thin'...........may be tht shud giv a clue.......

1
Anvay Vaidya ·

is the rod solid or hollow??????????????????????????????
there will be 2 different answers

62
Lokesh Verma ·

yes akand.. exactly :)

1
Akand ·

ohhhhhhhhhhhhhhhhhh ok............
then i dint take m/2..........

so my ans would be
moi= ((m/2)(l/2)2/3)*2........... rite???

1
~AjInKyA~ ·

but itz in considddrin thru centre an itz symetrix
i m not gud in rotataional but tatz how i solve prob >>>>
watz result righ or ronggggg?

1
Akand ·

so if i hav a bent or a straight or almost a circle type rod.........then moi is still ml2/12?????

62
Lokesh Verma ·

It should be ml2/12

Ajinkya's logic is correct!!

YOu could aslso consider it as 2 rods length L/2 and mass M/2 at the end points!

1
Rohan Ghosh ·

i dont think so akand

lets consider the rod as straight first

then moI = 2âˆ«r2dm

(for the two symmetrical halves)

when the rod is bent at any angle

it is stll the same as dm=always constant

and r=same for the two halves

1
~AjInKyA~ ·

it z wronggggggg ><><><>

1
~AjInKyA~ ·

hmmmmmmmm i dony think itz man!!!!
coz i know tat if suppose pizza symetrical !!!! of n pieces

and then if somepices are removed such tat remaininn pizza bcims symetric if considinggg a particular axis pasin inside it
then The moment of inertia is saMEEEEE

1
Pavithra Ramamoorthy ·

ya akand.. i think u r right..

1
Akand ·

u sure thts d rite ans????? then it may be correct....... i just solved wid sum stupid knowledge i had...............hehe
and thnx for teachin me new stuff...........

1
~AjInKyA~ ·

no akand itz simple logiccccc
Distribution of masses about axis of rotation remain unchanged whether it is straight or bend.
its symetrikkk
its m l2 / 12 the answr

1
Akand ·

earlier i had taken as m(l/2)2/12.........by mistake.........

1
Akand ·

so , its ml2/6................

1
Akand ·

sorry...........
m(l/2)2/3+m(l/2)2/3..........

1
~AjInKyA~ ·

i got it
its m l2 / 12 the answr
cozzzz Distribution of masses about axis of rotation remain unchanged whether it is straight or bend.
is tis logic righ!!!!!!!!!?

1
Pavithra Ramamoorthy ·

is dat 12?????