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# Question in GIKI 2012 Test

Question :

Sum of two vectors A and B is equal to A. Difference of these two vectors is equal to 2A. If A=4 find the MAGNITUDE of vector B.
a)3√2
b)6√2
c)2√6
d)3√6

Question of GIKI test 2012.

Solution:

In terms of rectangular components we can write:
A =√ A2x + A2y
B=√ B2x + B2y

Given:
A + B = A
it means

√( A2x + A2y ) +  √( B2x + B2y  ) =  4

Squaring Both sides, we get

A2x + A2y  +  B2x + B2  +  2√( A2x + A2y )( B2x + B2 ) =  16       (equation i)

Also
A-B = 2A
A-B = 8
√( A2x + A2y ) -  √( B2x + B2 ) =  8

Squaring Both sides, we get

A2x + A2y  +  B2x + B2  -  2√( A2x + A2y )( B2x + B2 ) =  64      (equation ii)

Adding equation i and ii we get

2(  A2x + A2y  +  B2x + B2y  ) =  80
16 + B2x + B2y = 40
B2x + B2y = 24
B2 = 24
B = √24 = √4x6 = 2√6

#### 10 comments:

1. what the hell was that? :O

2. @ayesha this was one of the question which was in test of GIKI last year :D

3. and this is the hardest and worst thing one would ever wish to see, if the test goes this way, we shouldnt even bother about studying for it because its already a fail fail attempt

4. well in Giki u have to face the questions like these . It will be teh hardest test u'll ever see . The way to get through this test is to clear ur concepts..

5. u substituted 16 but why ?
in last part of the question ?

6. magnitude of A is equal to 16 .

7. Awesome site you have here but I was curious if you knew
of any forums that cover the same topics talked about here?
I'd really like to be a [] part of community where I can get opinions from other experienced people that share the same interest. If you have any recommendations, please let me know. Thank you!

8. WE are supposed solve it in a minute?

9. we are supposed to solve it in a minute?

10. I have found a short method for this as well. Will add that too.

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