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NCERT Solutions for class 12 Maths | Chapter 10 - Vector Algebra

(1) If a, b, c are three mutually perpendicular vectors of equal magnitude, find the angle between a and a + b + c.
[A]
[B]
[C]
[D]
Answer:
(2) The dot product of a vector with the vectors are 0, 5 and 8 respectively. Find the vector.
[A]
[B]
[C]
[D]
Answer:

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(3) Find the value of λ so that the vectors are
[A] -15
[B] 10
[C] -40
[D] 20
Answer: -40
(4) If a, b, c are unit vectors, then |a – b| + |b – c| + |c – a| does not exceed
[A] 4
[B] 9
[C] 8
[D] 6
Answer: 9
(5) Find the value of λ if the vectors, a = and c = are coplanar.
[A] 4
[B] -2
[C] -6
[D] 5
Answer: 4
(6) If the vectors are coplanar, then the value
[A] 0
[B] 1
[C] 2
[D] 3
Answer: 0
(7) The volume of the parallelopiped whose edges are represented by and is 546 cu. units. Then α =
[A] 3
[B] 2
[C] -3
[D] -2
Answer: -3
(8) If the vectors form three concurrent edges of a parallelopiped, then the volume of the parallelopiped is
[A] 8
[B] 10
[C] 4
[D] 14
Answer: 4
(9) The volume of the tetrahedron whose conterminous edges are is
[A] 1/6 cu. unit
[B] 1/3 cu. unit
[C] 1/2 cu. unit
[D] 2/3 cu. unit
Answer: 1/3 cu. unit
(10) If u, v and w are three non-coplanar vectors, then (u + v – w).[(u – v) × (v – w)] equals
[A] 0
[B] u.v × w
[C] u.w × v
[D] 3u.v × w
Answer: u.v × w
(11) If a, b, c are three non-coplanar vectors, then (a + b + c).[(a + b) × (a + c)] is
[A] 0
[B] 2[abc]
[C] -[abc]
[D] [abc]
Answer: -[abc]
(12) If a is perpendicular to b and c, |a| = 2, |b| = 3, |c| = 4 and the angle between b and c is 2π/3, |abc| is equal to
[A] 4√3
[B] 6√3
[C] 12√3
[D] 18√3
Answer: 12√3
(13) The vector is rotated through an angle θ and doubled in magnitude, then it becomes The value of x is
[A] {−2/3,2}
[B] {1/3,2}
[C] {2/3,0}
[D] {2, 7}
Answer: {−2/3,2}
(14) The vectors and are collinear, if
[A] x =1, y = -2, z = -5
[B] x= 1.2, y = -4, z = -10
[C] x = -1/2, y = 4, z = 10
[D] All of these
Answer: All of these
(15) The vectors form the sides of
[A] Isosceles triangle
[B] Right triangle
[C] Scalene triangle
[D] Equilaterala triangle
Answer: Equilaterala triangle
(16) Find the magnitude of vector
[A] √157
[B] 4√11
[C] √213
[D] 9√3
Answer: √157
(17) If (1/2,1/3,n) are the direction cosines of a line, then the value of n is
[A] √23/6
[B] 23/6
[C] 2/3
[D] 3/2
Answer: √23/6
(18) The length of longer diagronai of the parallelogram constructed on 5a + 2b and a – 3b. If it is given that |a| = 2√2, |b| = 3 and angle between a and b is π4, is
[A] 15
[B] √113
[C] √593
[D] √369
Answer: √593
(19) If the angle between then the value of a is
[A] 0 or 2
[B] -4 or 0
[C] 0 or -3
[D] 2 or -2
Answer: -4 or 0
(20) If a and b are two unit vectors inclined to x-axis at angles 30° and 120° respectively, then |a + b| equals
[A]
[B] √2
[C] √3
[D] 2
Answer: 2

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