Super doubt..

i wonder y i never asked it before.....its my age old doubt.......but now i am going to prove sumthing.........

WHAT??? that neone who says that any vector has zero magnitude component in a direction perpendicular to it is horribly wrong....

see OA vector has component OB=OAcos a
OB has component OC perp to OA=OBsin a=OA(sin a)(cos a)=1/2OAsin 2a
thus OA has a component along perpendicular.....

bt that depends on value of angle a......it is zero if reference vector OB is taken 45° from OA..

but as all i also know this is wrong.....so where is the fallacy????

23 Answers

1
devika lal ·

i strongly believe that yu cant call da component of b(ie C) as da component of a just because b is a component of a

thats a wrong analogy

jagarans explanation is pretty appropriate:

consider B as X and line perpendicular to B as Y
you have 1st found components of A along X n Y
now you shift axes to C as X° and A as Y° and find components of B
obviously you get diff components....

1
Arka Halder ·

agree totally with swaraj.
OA has component OAsina in a direction perpendicular to OB.
That OAsina has a component OAsina.sin(90-a)=OAsina.cosa opposite to OC,thereby making the resultant in horizontal direction 0.

49
Subhomoy Bakshi ·

the soln of swaraj is exactly in resonance with my solution.................and my q wasn't wrong....LOLzzz

1
Che ·

"""see OA vector has component OB=OAcos a
OB has component OC perp to OA=OBsin a=OA(sin a)(cos a)=(1/2)OAsin 2a
thus OA has a component along perpendicular
"""

can any body tell me how u concluded tat OA has a component along OC

see its (1/2)OAsin2a.....so issey ye kahan prove ho raha hai ki OA has a component along OC

i mean teh doubt is itself rong ki u r saying tat u hav proved OA has a component along OC

1
devika lal ·

swaraj your explanation is pretty good

subhomoy pl put what solution you found...i guess most of us have completely deviated from what yu hav asked...
there are many ways of percepting the doubt n all da ppl hu hav given solns are right in their own way. your solution probably of a diff wavelength so tell us your thot process

62
Lokesh Verma ·

yup swaraj

Absolutely [1]

11
swaraj jena ·

hi subhomoy,first when u take the component of OA along OB u left the another component of OA which is along the axis perpendicular to OB . this component has also component along OC,which cancels ur above found component and the net component along OC becomes 0.

49
Subhomoy Bakshi ·

i give a hint here........itz something to do with something that we have missed out.....

LOL....all my hints are as usual graver and vaguer than my answer.....but anyways i start getting answers from the forum after such pokes only....

49
Subhomoy Bakshi ·

let me tell you all something you are arguing that the question is vague...but believe me neither my question nor my solution is vague......it is wrong.....no not wrong also but still there is some flaw.....tho it is not from books but i think this needs perception....

so lets find out the single change that needed to be made in the solution....as for the matter of fact i got the answer as soon as i wrote the question on my copy.....

try that process out...hope you all succeed like i did.....

21
eragon24 _Retired ·

hey tats actually quiet vague....the thing which u found out (OAsin2a)/2 tats actually teh component of OB NOT OA........ how r u saying it to be a component of OA ...i cant understand.......seriously....and it doesnt matter ki if u take out OB in terms of OA and then take component aLONG OC....then also it will remain component of OB not OA!

1
devika lal ·

da simplest explanation i can think of is tht when yu take component of b,it has one along a as well as along c
yu are calling da component of b along c as the component ofa...but in reality its da component along a tht shud be considered not c

49
Subhomoy Bakshi ·

Devika read my question correctly....i ask as we all know vector OC must be zero while we re getting different answers.....how do u explain.............

lol.....as i said the secret lies in something superficial yet deep:P:D

1
Jagaran Chowdhury ·

agts u have changed the axes of reference.thats where the mistake is

49
Subhomoy Bakshi ·

@debmalya: then ans comes -OA/2........
@nishant bhaiya: LOL....but still i'm not leaving it though......

62
Lokesh Verma ·

lol..

trust me even i had this idea once [4]

But this one is a good doubt to have :)

subhomoy, you will figure out as i keep doing, no matter how much you think you are innovating, it will be tough to come out with something no one else has done before ;)

1
debmalya760 ·

YOU HAVE TO PUT a=90°

49
Subhomoy Bakshi ·

no it is not vague....i have found out my mistake.....it is not as pointed out by others....the problem is more superficial yet deep

think india think!!![1][1][1][1][1][1][1]

1
devika lal ·

this one is vague

yu cant do tht bcoz once yu get da projection of a on b n then find da projection of b on c, yu are changing da vector of reference itself!

49
Subhomoy Bakshi ·

no one's answering this?????

49
Subhomoy Bakshi ·

i nw realise this could have been classified as one of <<<GOOGLY FROM ATGS>>>

49
Subhomoy Bakshi ·

but still everyone try this..........i swear it is really easy.....

49
Subhomoy Bakshi ·

yeah i got the answer..............really it is easy bt y did i not get earlier i wonder

49
Subhomoy Bakshi ·

when did i change axes????

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