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Anand Rananaware Grade: 11

1]If A = B+C and the magnitude of A, B and C are 5,4,3 unit, the angle between A and B is :

(a)cos-13/5                          (b) cos-14/5

(c)π/2                                    (d) sin-1 3/5

2] Unit vector parallel to the resultant of vectors 4i – 3j and 8i + 8j and 8i + 8j will be:

(a) (24i+5j)/13                   (b) (12i+5j)/13

(c) (6i+5j)/13                      (d) none of these

3] A force of 6 N and another of 8 N can be applied together to produce the effect of a single force of:

(a) 1 N                   (b) 11 N

(c) 15 N                 (d) 20 N

4] Two vectors having equal magnitudes A make an angle ? with each other. The magnitude and direction of the resultant are respectively:

(a) 2Acos ? /2, along bisector

(b) A cos ?/2, at 45 from one vector

(c) A cos ?/2, along bisector

(d) A sin ?/2, along bisector

6 years ago

Answers : (1)

AKASH GOYAL AskiitiansExpert-IITD
419 Points

Dear Anand

1. A-B=C square both sides

25+ 16-40 cos@=9  , cos@=32/40 = 4/5 ans b

2. resultant vector sum of all three = 20i + 13j  hence d

3. resultant square= 36 + 64 + 96 cos@= 100 + 96 cos@ range 4 to 196 

 resultant 2 to 16 answer b

4. R2= 2A2 + 2A2 COS@= 2A2 (1+COS@)=2A2 2COS2@/2

     R= 2ACOS@/2 option a


All the best.                                                           


AskiitiansExpert-IIT Delhi


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6 years ago
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