# Vector Algebra MCQs Part I

1) If a=4i+6j and b=3j+4k, then the vector form of component of a along
b is

a)
b)
c)
d) 3j+4k

2) The vector
is to be written as the sum of a vector parallel
to
and a vector

a)
b)
c)
d)

3) If

a) u is a unit vector
b) u=a+i+j+k
c) u=2a
d) u=8(i+j+k)

4) The volume of a parallelopiped whose sides are given by
is

a) 4/13
b) 4
c) 2/7
d) none of these

5) If then
the value of

a) 60
b) 64
c) 70
d) -74

6) The scalar
equals

a) 0
b) [ABC]+[BCA]
c) [ABC]
d) none of these

7) Let a=2i-j+k ; b=i+2j-k and c=i+j+2k be three vectors. A vector in the plane
of
b and c whose projection on a is of magnitude
is

a) 2i-3j-3k
b) 2i+3j+3k
c) -2i-j+5k
d) 2i+j+5k

8) If the vectors c, a=xi+yj+zk and b=j are such that a, c, b form a right
handed systems then c is

a) zi-xk
b) 0
c) yj
d) -zi+xk

9) ABCD is a quadrilateral with
If its area is times the area
of adjacent sides, then is equal
to

a) 5
b)
c) 1
d)

10) ABCDEF is a regular hexagon where center O is the origin. If the position
vectors of A and B are respectively
the is equal to

a)
b)
c)
d) none of these

11) The position vectors of two vertices and the centroid of a triangle are
. The position vector of the
third vertex of the triangle is

a)
b)
c)
d) none of these

12) Let the position vectors of the point A,B,C be
respectively. Then the ABC is

a) right angled
b) equilateral
c) isosceles
d) none of these

13) . are three vectors of which
every pair is noncollinear. If the vector
are collinear with

a) a unit vector
b) the null vector
c)
d) none of these

14)
a)
b)
c)
d)

15) The position vectors of three points are
and are noncoplanar vectors. The
points are collinear when

a)
b)
c)
d) None of these

16) are linearly dependent
vectors and then

a)
b)
c)
d)

17) Let A vectors along one of the
bisectors of the angle <AOB is

a)
b)
c)
d) none of these

18) A vector has components 2p and 1 with respect to a rectangular Cartesian
system. The axes are rotated through an angle
about the origin in the anticlockwise sense. If the vector has components
p+1 and 1 with respect to the new system then

a)
b) p=0
c)
d) p=1,-1

19) If are two vectors of magnitude
2 inclined at an angle then
the angle between is

a)
b)
c)
d) None of these

20) Let Then the angle between

a)
b)
c)
d)

21) A vector of magnitude 4 which is equally inclined to the vectors
a)
b)
c)
d) none of these

22) If
a)
b)
c)
d) none of these

23) Let is
a)
b) 6
c)
d) none of these

24)
a)
b)
c)
d) none of these

25) If
are unit vectors such that
is also a unit vector then the angle between the vectors

a)
b)
c)
d)

26)
a)
b)
c)
d)

27) is
equal to

a)
b) 3
c)
d) none of these

28) is
equal to

a)
b) 0
c)
d) none of these

29) If a,b,c are the pth, qth, rth terms of an HP andthen
a)
b)
c)
d)

30) If
a)
b)
c)
d)

31) Let
a)
b)
c)
d)

32) Let
a)
b)
c)
d) none of these

33) If are
three vectors of equal magnitude and the angle between each pair of vectors
is
such that
is equal to

a) 2
b) -1
c) 1
d)

34) If
a) 1
b)
c) 3
d) none of these

35) If
equal to

a)
b)
c)
d) none of these

36) If
a)
b)
c)
d) none of these

37) Two vectors
a) perpendicular to each other
b) parallel to each other
c)
d)

38) ABC is an equilateral triangle of side a. the value of
a)
b)
c)
d) none of these

39) If
a)
b)
c)
d) none of these

40)
a) 0
b)
c)
d) 1

41) If
are two noncollinear and nonzero vectors such that where,
a,b,c are the lengths of the sides of a triangle, then the triangle is

a) right angled
b) obtuse angled
c) equilateral
d) isosceles

42) If
are any three vectors such that is

a)
b)
c)
d) none of these

43) Let
a) 1
b) 0
c) -1
d) 2

44) The vectors are
the sides of a triangle which is

a) equilateral
b) isosceles
c) right angled
d) both b and c

45)
a)
b)
c)
d)

46)
a) an equilateral triangle
b) a right angled triangle
c) an isosceles triangle
d) collinear vectors

47)
a) -3/2
b) 0
c) -1
d) 1

48) Let
a)
b)
c)
d)

49) What is the value of
a) 0
b)
c)
d)

50) The position vectors of the points A and B are
respectively. P divides AB in the ratio 3 : 1. Q is the mid-point of AP. The
position vector of Q is

a)
b)
c)
d)

51)
a) -1
b) 0
c) 2
d) -3

52)
a)
b)
c)
d) none of these

53)
a)
b)
c)
d) none of these

54)
a) 0
b) 1
c)
d)

55) A vector
has components 2p and 1 with respect to a rectangular Cartesian system. This
system is rotated through a certain angle about the origin in the counterclockwise
sense. If, with respect to the new system,
has components p+1 and 1, then

a) p = 0
b)
c)
d) p = 1 or p = -1

56)
a) 0
b) 1
c) 2
d) -2

57) The angle between vectors
a)
b)
c)
d) 0

58)

are
vectors reciprocal to the non-coplanar vectors
then

a)
b) 1
c) 4
d) 0

59) Let be
three non-coplanar vectors and
are vectors defined by the relations
Then the value of the expression

a) 0
b) 1
c) 2
d) 3

60) The value of
a)
b)
c)
d) 0

61) Which one of the following is not a vector?
a) Momentum
b) Velocity
c) Mass
d) Angular velocity

62) What is needed to represent a scalar?
a) a real number only
b) a real number and a unit of measurement
c) a unit of measurement only
d) none of these

63) The magnitude of a vector is
a) unique
b) not unique
c) a unique positive integer
d) not unique but can have only finite number of values

64) If is a unit vector ^
r to , then the second unit vector
^ r  to
is

a)
b)
c)
d)

65) The projection of on OX, OY,
OZ are respectively 12, 3 and 4, then the magnitude of
is

a) 13
b) 169
c) 19
d) 16

66) The angle between the straight lines

a) 0
b)
c)
d)

67) The volume ( in cubic units) of the parallelopiped whose edges are represented
by the vectors

a) 2
b) 0
c)
d)

68) A unit vector normal to the plane through the points
a)
b)
c)
d) none

69) The work done by the force
in moving a particle along a straight line from the point
(3,2,-1) to (2, -1,4) is

a) 0
b) 4
c) 15
d) 19

70) Two like parallel forces P and 3P act on a rigid body at points A and B
respectively. If the forces are interchanged in position, the resultant will
be displaced through a distance of

a)
b)
c)
d)

71) Let
If the point of P on the line segment BC is equidistant from AB and AC then
is

a)
b)
c)
d) none of these

72) Two vectors are said to be equal if
a) their magnitudes are same
b) direction same
c) originate from the same point
d) they have same magnitude and same sense of direction

73) Two vectors a and b are parallel and have equal magnitudes, then
a) they are equal
b) they are not equal
c) they may or not be equal
d) they do not have the same direction

74) If a is non-zero vector of modulus a and m is a non-zero scalar,
then m a is a unit vector if

a)
b)
c)
d) none

75) a and b are two unit vectors and
is the angle between them. Then a+b is a unit vector if

a)
b)
c)
d)

76) The position vectors of A and B are a and b respectively,
then the position vector of a point P which divides AB in the ratio
1:2 is

a)
b)
c)
d)

77) Point A is a+2b, P is a and P divides AB in the ratio 2:3. The position
vector of B is

a) 2a-b
b) b-2a
c) a-3b
d) b

78)
is the angle between the two vectors a and b then

a)
b)
c)
d)

79) If a be a non-zero vector then which of the following is correct?
a) a . a = 0
b) a . a > 0
c)
d)

80) a and b are two non-zero vectors, then (a+b).(a-b) is equal to
a) a + b
b)
c)
d)

81) a.b=0 implies only
a) a=0
b) b=0
c)
d)

82) If a,b,c be three non-zero vectors then the equation a.b=a.c implies
a) b=c
b) a is orthogonal to both b and c
c) a is orthogonal to b-c
d) either b=c or a is orthogonal to b-c

83) If a and b include an angle of
and their magnitudes are 2 and ,
then a.b is equal to

a) 3
b)
c)
d) -3

84) If (i, j, k) be a set of orthogonal unit vectors, then
a) i.i+j.j+k.k=0
b) i.j+j.k+k.i=3
c) i.i=j.j=k.k=1
d) i.j=j.k=k.i=1

85) If
be the angle between the vectors 4(i-k) and i+j+k, then
is

a)
b)
c)
d)

86) The angle between the vectors 2i+ 3j+ k and 2i-j-k is
a)
b)
c)
d) 0

87) If a and b are two vectors, then
is a unit vector if

a)
b)
c)
d) none

88) [a b c] is the scalar triple product of three vectors, a, b and c, then
[a b c] is equal to

a) [b a c]
b) [c b a]
c) [b c a]
d) [a c b]

89) If
is the angle between vectors a and b, then
is equal to

a) 0
b)
c)
d)

90)
is equal to

a) (a.b)c-(b.c)b
b) (a.b)a+(a.b)c
c) (b.c)a-(b.c)b
d) (a.c)b-(a.b)c

91) ,
then

a) u is a unit vector
b) u=a+b+c
c) u=0
d)

92) If a= 4i+2j-5k, b=-12i-6j+15k, then the vectors a, b are
a) orthogonal
b) parallel
c) non-coplanar
d) none of these

93) If [i, j, k] be orthogonal set of unit vectors, then
a)
b)
c)
d)

94) If the position vectors of three points are, a-2b+3c, 2a+3b-4c, -7b+10c,
then the three points are

a) collinear
b) coplanar
c) non-collinear
d) neither

95) If a+b+c=0, then
the angle between a and b is

a)
b)
c)
d)

96) If a, b, c are any three coplanar unit vectors, then
a)
b)
c)
d)

97) If a.b=a.c and
then

a) a is perpendicular to b-c
b) a is parellel to b-c
c) either a=0 or b=c
d) none of these

98) If
then (a+b).(a-b) is

a) +ive
b) -ive
c) zero
d) none of these

99) The vector 2i+j-k is perpendicular to i-4j+,
if
is equal to

a) 0
b) -1
c) -2
d) -3

100) The area of parallelogram having diagonals a=3i+j-2k and b=i-3j+4k is
a)
b)
c) 8
d) 4

Ans 1) b
Note that the component of vector a along the vector b is
Ans Desc 1)
Note that the component of vector a along the vector b is

Ans 2) a

Any vector perpendicular to A

Ans Desc 2)

Any vector perpendicular to A

Ans 3) c

Ans 4) b

Ans 5) d

Ans 6) a

Ans 7) c
Any vector r in the plane of b and c is r=b+tc
or r(1+t)i+(2+t)j-(1+2t)k

Ans Desc 7)
Any vector r in the plane of b and c is r=b+tc
or r(1+t)i+(2+t)j-(1+2t)k

Ans 8) a

Since a, c, b form a right handed system

Ans Desc 8)

Since a, c, b form a right handed system

Ans 9) b

= Area of

Ans Desc 9)

= Area of

Ans 10) b

=.

Ans Desc 10)

=.

Ans 11) a
The positive vector of the centroid =
are the position vectors ofo the vertices.

Ans Desc 11)
The positive vector of the centroid =
are the position vectors ofo the vertices.

Ans 12) b

Similarly, find

Ans Desc 12)

Similarly, find

Ans 13) b
Here, Subtracting,

or
But are noncollinear.

Ans Desc 13)
Here, Subtracting,

or
But are noncollinear.

Ans 14) a

Solving these, are in AP.

Ans Desc 14)

Solving these, are in AP.

Ans 15) c

If the point be A, B and C respectively then

The points are collinear if

Ans Desc 15)

If the point be A, B and C respectively then

The points are collinear if

Ans 16) d
Here,
Now

and

Ans Desc 16)
Here,
Now

and

Ans 17) c

Ans 18) a
Here, . After rotation, let
the vector be
Then But the magnitude of
a vector does nto change with rotation of axes.

Ans Desc 18)
Here, . After rotation, let
the vector be
Then But the magnitude of
a vector does nto change with rotation of axes.

Ans 19) a
Here,
If the angle between

or
or

Now,
=4+4+2.2=12

Ans Desc 19)
Here,
If the angle between

or
or

Now,
=4+4+2.2=12

Ans 20) b
1=

or

Ans Desc 20)
1=

or

Ans 21) c
Let
Now, (from the question)
or x+y=y+z=z+x=t (say).

Ans Desc 21)
Let
Now, (from the question)
or x+y=y+z=z+x=t (say).

Ans 22) b

So,

Ans Desc 22)

So,

Ans 23) a

Similarly, we get

=1+2+3+0=6

Ans Desc 23)

Similarly, we get

=1+2+3+0=6

Ans 24) b
Let
Ans Desc 24)
Let

Ans 25) d

and are
unit vectors.
Angle
between a and b is 1200.

Ans Desc 25)

and are
unit vectors.
Angle
between a and b is 1200.

Ans 26) b

Ans Desc 26)

Ans 27) a
See the hint to Q. NO. 15 As

Ans Desc 27)
See the hint to Q. NO. 15 As

Ans 28) a
a2 + b2 + 2ab – (a2 + b2
2ab) = 4ab = 4 a.b

Ans Desc 28)
a2 + b2 + 2ab – (a2 + b2
2ab) = 4ab = 4 a.b

Ans 29) b

From the question,
Putting these in (1) and simplifying,
Clearly,

Ans Desc 29)

From the question,
Putting these in (1) and simplifying,
Clearly,

Ans 30) b
Here
or

Ans Desc 30)
Here
or

Ans 31) a

(given)
Now,

and
or 6t+3s=0or2t+s=0.

or

Ans Desc 31)

(given)
Now,

and
or 6t+3s=0or2t+s=0.

or

Ans 32) b
therefore,
they are coplanar.

Ans Desc 32)
therefore,
they are coplanar.

Ans 33) c

Then

Similarly,
Now, 6=

Ans Desc 33)

Then

Similarly,
Now, 6=

Ans 34) b

Ans Desc 34)

Ans 35) a

or

Ans Desc 35)

or

Ans 36) b
By condition.
Ans Desc 36)
By condition.

Ans 37) d

Or

Ans Desc 37)

Or

Ans 38) c

or

Ans Desc 38)

or

Ans 39) a
Here,

Ans Desc 39)
Here,

Ans 40) b

these.

Ans Desc 40)

these.

Ans 41) c
are
noncoplanar. Therefore, the given linear relation is possible only when b-c=0,
c-a=0, a-b=0. So, a=b=c.

Ans Desc 41)
are
noncoplanar. Therefore, the given linear relation is possible only when b-c=0,
c-a=0, a-b=0. So, a=b=c.

Ans 42) a

Ans Desc 42)

Ans 43) b

or
or
or

Ans Desc 43)

or
or
or

Ans 44) d

Ans Desc 44)

Ans 45) a

Ans Desc 45)

Ans 46) b

Ans Desc 46)

Ans 47) a

Ans Desc 47)

Ans 48) c

Ans Desc 48)

Ans 49) c

Ans Desc 49)

Ans 50) a

Ans Desc 50)

Ans 51) c

Ans Desc 51)

Ans 52) b

Ans Desc 52)

Ans 53) c

Ans Desc 53)

Ans 54) c

Ans Desc 54)

Ans 55) b
Let
make angle
with the original axes. Let the original co-ordinate system be rotated through
angle

Ans Desc 55)
Let
make angle
with the original axes. Let the original co-ordinate system be rotated through
angle

Ans 56) d

Ans Desc 56)

Ans 57) a

Ans Desc 57)

Ans 58) b

Ans Desc 58)

Ans 59) d

Ans Desc 59)

Ans 60) c

The value of

Ans Desc 60)

The value of

Ans 61) c

Ans 62) b

Ans 63) c

Ans 64) c

Ans 65) a
Projections of the line joining

Ans Desc 65)
Projections of the line joining

Ans 66) c

Ans Desc 66)

Ans 67) a

Ans Desc 67)

Ans 68) c

Ans Desc 68)

Ans 69) c
Let be the force and A and B
be the given points

Ans Desc 69)
Let be the force and A and B
be the given points

Ans 70) a

In the first case, if the resultant acts at C, then

In the second case, if the resultant act at D, then

Ans Desc 70)

In the first case, if the resultant acts at C, then

In the second case, if the resultant act at D, then

Ans 71) c

Ans Desc 71)

Ans 72) d

Ans 73) d
Parallel does not imply that the same sense of direction. Hence they are
equal if the sense of direction is same and not equal if the sense of the
direction is opposite. Hence (d) is the correct answer.

Ans Desc 73)
Parallel does not imply that the same sense of direction. Hence they are
equal if the sense of direction is same and not equal if the sense of the
direction is opposite. Hence (d) is the correct answer.

Ans 74) c
a is the modulus of vector a. Modulus is ma is
Ans Desc 74)
a is the modulus of vector a. Modulus is ma is

Ans 75) d
a+b is unit vector if

Ans Desc 75)
a+b is unit vector if

Ans 76) b
Since by
section formula.

Ans Desc 76)
Since by
section formula.

Ans 77) c

Ans Desc 77)

Ans 78) c

Ans Desc 78)

Ans 79) b
Square of vector is square of its modulus
Ans Desc 79)
Square of vector is square of its modulus

Ans 80) d

Ans Desc 80)

Ans 81) d

Ans 82) d
. It
follows that a is orthogonal to b-c or b-c =0 i.e., b=c or a=0. But a is non-zero
vector. Hence the correct answer is (d) which includes all the above cases.

Ans Desc 82)
. It
follows that a is orthogonal to b-c or b-c =0 i.e., b=c or a=0. But a is non-zero
vector. Hence the correct answer is (d) which includes all the above cases.

Ans 83) b

Ans Desc 83)

Ans 84) c
Since i.i=1=j.j=k.k
Ans Desc 84)
Since i.i=1=j.j=k.k

Ans 85) c

Ans Desc 85)

Ans 86) a

Ans 87) b

Ans Desc 87)

Ans 88) c
Scalar triple product remains unchanged if cyclic order is maintained.
Ans Desc 88)
Scalar triple product remains unchanged if cyclic order is maintained.

Ans 89) d

Ans Desc 89)

Ans 90) d

Ans 91) c
Check yourself. Since
Ans Desc 91)
Check yourself. Since

Ans 92) b

Ans 93) b
Since
Ans Desc 93)
Since

Ans 94) a
If A, B, C are the two points, then
and so A, B, C are collinear.

Ans Desc 94)
If A, B, C are the two points, then
and so A, B, C are collinear.

Ans 95) d

Ans Desc 95)

Ans 96) c

Ans 97) c

Ans 98) c

Ans 99) c

Ans 100) b

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