Vector Algebra
Question
Question 1 : If a, b and c be non-zero vectors, then which of the following statements is correct?
1. a x (b - c) = (c - b) x a
2. a
. (b + c) = (c + b)
. a
3. a x (b + c) = (c + b) x a
4. a
. (b - c) = (c - b)
. a
Answer
Correct Anaswer : 1
Explanation:
Options (b) and (d) are ruled out because dot product is commutative and option (c) is ruled out as cross-product is not commutative.
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Question 2 : The area, of the parallelogram having diagonals
d1 = 3 i + j - 2k and d2 = i - 3j + 4k is
1. 10√3
2. 5√3
3. 8
4. 4
Answer
Correct Anaswer : 2
Explanation:
Area =(1/2) |d1 x d2| = (1/2) x 10√3 = 5√3
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Question 3 : If position vectors of four points A, B, C and D are i + j + k, 2i + 3j, 3i + 5j - 2k and k - j respectively, then AB and CD are related as
1. perpendicular
2. parallel
3. independent
4. none of these
Answer
Correct Anaswer : 2
Explanation:
AB = i + 2j - k
CD = -3 (i + 2j - k) = -3AB
Therefore, AB and CD are parallel
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Question 4 : Consider four points P, Q, R and S with their position vector - (j + k), 4i + 5j + λk, 3i + 9j + 4k and - 4i + 4j + 4k, respectively. If |PQ| = |QR|, then λ is equal to ?
1. 1
2. - 1
3. 2
4. - 2
Answer
Correct Anaswer : 4
Explanation:
-2
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Question 5 : What is the vector perpendicular to both the vectors i - j and i?
1. i
2. - j
3. j
4. k
Answer
Correct Anaswer : 4
Explanation:
The vector perpendicular to both the vectors
(i - j) and
i = (i - j) x i
= i x i - j x i
= 0 + i x j = k
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