1
NDA 2018 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
A unit vector perpendicular to each of the vectors $$2\widehat i - \widehat j + \widehat k$$ and $$3\widehat i - 4\widehat j - \widehat k$$ is
A
$${1 \over {\sqrt 3 }}\widehat i + {1 \over {\sqrt 3 }}\widehat j - {1 \over {\sqrt 3 }}\widehat k$$
B
$${1 \over {\sqrt 2 }}\widehat i + {1 \over 2}\widehat j + {1 \over 2}\widehat k$$
C
$${1 \over {\sqrt 3 }}\widehat i - {1 \over {\sqrt 3 }}\widehat j - {1 \over {\sqrt 3 }}\widehat k$$
D
$${1 \over {\sqrt 3 }}\widehat i + {1 \over {\sqrt 3 }}\widehat j + {1 \over {\sqrt 3 }}\widehat k$$
2
NDA 2018 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
If | a | = 3, | b | = 4 and | a $$-$$ b | = 5, then what is the value of | a + b | ?
A
8
B
6
C
5$${\sqrt 2 }$$
D
5
3
NDA 2018 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
Let a, b and c be three mutually perpendicular vectors each of unit magnitude. If

A = a + b + c, b = a $$-$$ b + c and C = a $$-$$ b $$-$$ c, then which one of the following is correct?
A
| A | > | B | > | C |
B
| A | = | B | $$\ne$$ | C |
C
| A | = | B | = | C |
D
| A | $$\ne$$ | B | $$\ne$$ | C |
4
NDA 2018 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
What is (a $$-$$ b) $$\times$$ (a + b) equal to ?
A
0
B
a $$\times$$ b
C
2 (a $$\times$$ b)
D
| a |2 $$-$$ | b |2
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