If three unit vectors a→, b→, c→ sa

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 Multiple Choice QuestionsMultiple Choice Questions

431.

The volume (in cubic units) of the tetrahedron with edges i^ + j^ +k^,  i^ -  j^ +k^ and  i^ + 2j^ - k^ is 

  • 4

  • 23

  • 16

  • 13


432.

Let a = a1i^ +a2j^ + a3k^Assertion A : The identitya × i^2 +a × j^2 + a × k^2 = 2a2 holds for  aReason R : a × i^ = a3j^ - a2k^,a × j^ = a1k^ - a3i^,  a × k^ = a2i^ - a1j^Wich of the following is correct ?

  • Both (A) and (R) are true and (R) is the correct reason for (A)

  • Both (A) and (R) are true but (R) is not the correct reason for (A)

  • (A) is true, (R) is false

  • A) is false, (R) is true


433.

The position vectors of P and Q are a and b respectively. If R is a point on PQ such that PR = 5PQ, then the position vector of R is

  • 5b - 4a

  • 5b + 4a

  • 4b - 5a

  • 4b + 5a


434.

If the points with position vectors 60i^ + 3j^, 40i^ - 8j^ and ai^ - 52j^ are collinear, then a is equal to  are collinear,then a is equal to

  • - 40

  • - 20

  • 20

  • 40


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435.

If the position vectors of A, B and C are respectively 2I^ - J^ + K^, I^ - 3J^ - 5K^ and 3i^ - 4j^ - 4k^, then cos2A = ? 

  • 0

  • 641

  • 3541

  • 1


436.

Let a be a unit vector,  b = 2i^ + j^ - k^ and c =i^ + 3k^. Then, maximum value of[a b c] is

  • - 1

  • 10 + 6

  • 10 - 6

  • 59


 Multiple Choice QuestionsMatch The Following

437.

If a = i^ + j^ + k^, b = i^ - j^ + k^, c = i^ + j^ - k^ and d =i^ - j^ - k^, then observe the following lists
  List-I   List-II
(i) a . b (A) a . d
(ii) b . c (B) 3
(iii) a b c (C) b . d
(iv) b × c (D) 2i^ - k^
    (E) 2j^ + 2k^
    (F) 4

Then, correct match of List_I to List-II is

A. (i) (ii) (iii) (iv) (i) C A B F
B. (i) (ii) (iii) (iv) (ii) C A F E
C. (i) (ii) (iii) (iv) (iii) A C B F
D. (i) (ii) (iii) (iv) (iv) A C F D

 Multiple Choice QuestionsMultiple Choice Questions

438.

If m1, m2, m3 and m4 are respectively the magnitudes of the vectorsa1 = 2i^ - j^ + k^, a2 = 3i^ - 4j^ - 4k^,a3 = i^ + j^ - k^ and  a4 = - i^ +  3j^ + k^, then the correct order of m1, m2, m3 and m4 is 

  • m3 < m1 < m4 < m2

  • m3 < m1 < m2 < m4

  • m3 < m4 < m1 < m2

  • m3 < m4 < m2 < m1


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439.

Let a = i^ - 2j^ + 3k^, b = 2i^ + 3j^ - k^, c = i^ - 2j^ + 3k^. If c is parallel to the plane containing a, b, then λ is equal to

  • 0

  • 1

  • - 1

  • 2


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440.

If three unit vectors a, b, c satisfy a + b + c, then the angle between a and b is

  • 2π3

  • 5π6

  • π3

  • π6


A.

2π3

Given condition isa + b + c = 0   ... iand a,  b, c are the unit vectorsThen a = b = c = 1Let the angle between a and b is θNow, from eq. ia + b + c = 0  a + b  = - cSquaring on both sides a + b2 =  c2       c2  = c2    a2 + b2  + 2a  . b = c2 a2 + b2 + 2a  . b = c2 1 + 1 + 2 abcosθ = 1      a . b = abcosθ 2(1 1 . cosθ) = - 1  cosθ = cos2π3 θ = 2π3


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