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Vectors

Cool goIITian

 Joined: 29 May 2012 Post: 32
8 Jun 2012 20:52:45 IST
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Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Vectors

two forces equal in magnitude act at a point simultaneously. the magnitude of the resultant of two forces is equal to the magnitude of either.the angle bettween two forces is...?? please i want the answer as soon as possible with method please..

Scorching goIITian

Joined: 5 May 2012
Posts: 218
8 Jun 2012 21:24:04 IST
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We know that the magnitude of the resultant of two vectors is given by the formula:

where is the angle between the two vectors. It is given that all three vecors have same magnitude, so let each vector have magnitude A. Then, we can solve for ,

Solving for , we get

=>

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Cool goIITian

Joined: 29 May 2012
Posts: 32
8 Jun 2012 21:42:29 IST
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hey thnx ya i got it

Forum Expert
Joined: 29 Dec 2006
Posts: 5535
9 Jun 2012 15:29:59 IST
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If the magnitude of two forces and resultant is x then x^2 = x^2 + x^2 + 2x^2xcos(@) where @ is angle between two vectors. By solving we get cos(@) = -1/2 or @ = 120 degree

Hot goIITian

Joined: 1 Sep 2011
Posts: 101
21 Jun 2012 08:26:59 IST
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remenmber the rule this is a special case !!!!! in this case the angle will lways be 120 degress

New kid on the Block

Joined: 22 Jun 2012
Posts: 6
22 Jun 2012 04:21:18 IST
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Another method is..if 2 forces r equal n resultant's mag. Equals force so by triangle law its equilateral triangle..n then as we know if head of 1vector is with tail of other angle taken is external 1 so 180-60=120 degree.. Hope uh got it!! Else i will explain further..

New kid on the Block

Joined: 22 Jun 2012
Posts: 6
22 Jun 2012 04:22:40 IST
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@Batra we cant say this any special case.. its going acc. To rules n laws of vectors so saying it special case makes different sense

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