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Vector Algebra

JEE Main 2024 (Online) 9th April Morning ShiftMCQMedium📈 Topic in 59% papers+4−1
Ques. 1JEE Main 2024, 9 April (Morning Shift)

Let OA = 2 a, OB = 6 a + 5 b and OC = 3 b, where O is the origin. If the area of the parallelogram with adjacent sides OA and OC is 15 sq. units, then the area (in sq. units) of the quadrilateral OABC is equal to:

  1. 32
  2. 38
  3. 35
  4. 40

Answer

(3) 35

Solution

[figure]

The parallelogram on OA and OC has area 15, so |2 a 3 b| = 15, i.e. | a b| = 52.

The area of a quadrilateral is half the magnitude of the cross product of its diagonals. Here OB = 6 a + 5 b and AC = OC - OA = 3 b - 2 a (dashed), so

Area = 12 |(6 a + 5 b) (3 b - 2 a) |

= 12 |18 a b - 10 b a | (since a a = b b = 0)

= 12 28| a b| = 14 52 = 35

Answer: (3)

Keep practising — Vector Algebra

Ques. 2JEE Main 2024, 9 April (Evening Shift)

Between the following two statements:

  1. Both Statement I and Statement II are correct.
  2. Both Statement I and Statement II are incorrect.
  3. Statement I is correct but Statement II is incorrect.
  4. Statement I is incorrect but Statement II is correct.
Ques. 3JEE Main 2024, 9 April (Evening Shift)

Let a = 2 i + j + k, b = - i + k, c = j - k, where and are integers and = -6. Let the values of the ordered pair ( , ), for which the area of the parallelogram of diagonals a + b and b + c is 212, be ( 1, 1) and ( 2, 2). Then 12 + 12 - 2 2 is equal to

  1. 21
  2. 24
  3. 19
  4. 17
Ques. 4JEE Main 2024, 8 April (Morning Shift)

The set of all , for which the vectors a = t i + 6 j - 3 k and b = t i - 2 j - 2 t k are inclined at an obtuse angle for all t R, is

  1. [0, 1)
  2. (- 43, 0 ]
  3. (-2, 0]
  4. (- 43, 1 )
Ques. 5JEE Main 2024, 8 April (Morning Shift)

Let a = 9 i - 13 j + 25 k, b = 3 i + 7 j - 13 k and c = 17 i - 2 j + k be three given vectors. If r is a vector such that r a = ( b + c) a and r ( b - c) = 0, then |593 r + 67 a|2(593)2 is equal to .

Ques. 6JEE Main 2024, 8 April (Evening Shift)

Let a = 4 i - j + k, b = 11 i - j + k and c be a vector such that ( a + b) c = c (-2 a + 3 b). If (2 a + 3 b) c = 1670, then | c|2 is equal to:

  1. 1600
  2. 1618
  3. 1627
  4. 1609
Ques. 7JEE Main 2024, 8 April (Evening Shift)

Let a = i + 2 j + 3 k, b = 2 i + 3 j - 5 k and c = 3 i - j + k be three vectors. Let r be a unit vector along b + c. If r a = 3, then 3 is equal to:

  1. 21
  2. 25
  3. 27
  4. 30
Ques. 8JEE Main 2024, 6 April (Morning Shift)

If A(3, 1, -1), B ( 53, 73, 13 ), C(2, 2, 1) and D ( 103, 23, -13 ) are the vertices of a quadrilateral ABCD, then its area is

  1. 4 23
  2. 2 23
  3. 5 23
  4. 2 2
Ques. 9JEE Main 2024, 6 April (Morning Shift)

Let a = 2 i - 3 j + 4 k, b = 3 i + 4 j - 5 k and a vector c be such that a ( b + c ) + b c = i + 8 j + 13 k. If a c = 13, then (24 - b c ) is equal to .

Ques. 10JEE Main 2024, 6 April (Evening Shift)

Let a = 2 i + j - k, b = (( a ( i + j)) i) i. Then the square of the projection of a on b is:

  1. 13
  2. 15
  3. 2
  4. 23
Ques. 11JEE Main 2024, 6 April (Evening Shift)

Let a = 6 i + j - k and b = i + j. If c is a vector such that | c| 6, a c = 6| c|, | c - a| = 2 2 and the angle between a b and c is 60 , then |( a b) c| is equal to:

  1. 32 6
  2. 92(6 - 6)
  3. 92(6 + 6)
  4. 32 3

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