Vector Algebra

Let a=a1 i+a2 j+a3 k and b=b1 i+b2 j+b3 k be two vectors such that | a|=1, a b=2 and | b|=4. If c=2( a b)-3 b, then the angle between b and c is equal to:

1. -1 (- 1 3 )
2. -1 ( 23 )
3. -1 ( 2 3 )
4. -1 (- 32 )

Let A(2,3,5) and C(-3,4,-2) be opposite vertices of a parallelogram ABCD. If the diagonal BD= i+2 j+3 k, then the area of the parallelogram is equal to :

1. 12 410
2. 12 306
3. 12 586
4. 12 474

Let a= i+ j+ k, , R. Let a vector b be such that the angle between a and b is 4 and | b|2=6. If a b=3 2, then the value of ( 2+ 2 )| a b|2 is equal to

1. 85
2. 90
3. 75
4. 95

Let a and b be two vectors such that | b|=1 and | b a|=2. Then |( b a)- b|2 is equal to

1. 1
2. 3
3. 5
4. 4

Let a, b and c be three non-zero vectors such that b and c are non-collinear. If a+5 b is collinear with c, b+6 c is collinear with a and a+ b+ c= 0, then + is equal to

1. 30
2. -30
3. -25
4. 35

Let O be the origin and the position vectors of A and B be 2 i+2 j+ k and 2 i+4 j+4 k respectively. If the internal bisector of meets the line AB at C, then the length of OC is

1. 32 34
2. 23 31
3. 23 34
4. 32 31

Let a unit vector u=x i+y j+z k make angles 2, 3 and 2 3 with the vectors 1 2 i+ 1 2 k, 1 2 j+ 1 2 k and 1 2 i+ 1 2 j respectively. If v= 1 2 i+ 1 2 j+ 1 2 k then | u- v|2 is equal to

1. 112
2. 52
3. 7
4. 9

Let OA= a, OB=12 a+4 b and OC= b, where O is the origin. If S is the parallelogram with adjacent sides OA and OC, then area of the quadrilateral OABCarea of S is equal to .

1. 7
2. 6
3. 8
4. 10

Let a= i+2 j+ k, b=3( i- j+ k). Let c be the vector such that a c= b and a c=3. Then a (( c b)- b- c) is equal to :

1. 32
2. 36
3. 24
4. 20

The least positive integral value of , for which the angle between the vectors i-2 j+2 k and i+2 j-2 k is acute, is .