NDA & NA Exam (II)- 2017 - Mathematics Defence Question Paper

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NDA & NA Exam (II)- 2017 - Mathematics

NDA & NA Exam (II)- 2017 - Mathematics Defence Questions

41.
The points (a, b), (0, 0), (−a, −b) and \( (ab, b^{2}) \) are
A.
the vertices of a parallelogram
B.
the vertices of a rectangle
C.
the vertices of a square
D.
collinear
ANSWER :
D. collinear
42.
The length of the normal from origin to the plane \( x + 2y - 2z = 9 \) is equal to
A.
2 units
B.
3 units
C.
4 units
D.
5 units
ANSWER :
B. 3 units
43.
If \( \alpha \), \( \beta \) and \( \gamma \) are the angles which the vector \( \overrightarrow{OP} \) (O being the origin) makes with positive direction of the coordinate axes, then which of the following are correct?
1. \( \cos^{2}\alpha + \cos^{2}\beta = \sin^{2}\gamma \)
2. \( \sin^{2}\alpha + \sin^{2}\beta = \cos^{2}\gamma \)
3. \( \sin^{2}\alpha + \sin^{2}\beta + \sin^{2}\gamma = 2 \)
Select the correct answer using the code given below.
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
C. 1 and 3 only
44.
The angle between the lines \( x + y - 3 = 0 \) and \( x - y + 3 = 0 \) is \( \alpha \) and the acute angle between the lines \( x - \sqrt{3}y + 2\sqrt{3} = 0 \) and \( \sqrt{3}x - y + 1 = 0 \) is \( \beta \). Which one of the following is correct?
A.
\( \alpha = \beta \)
B.
\( \alpha > \beta \)
C.
\( \alpha < \beta \)
D.
\( \alpha = 2\beta \)
ANSWER :
B. \( \alpha > \beta \)
45.
Let \( \vec{\alpha} = \hat{i} + 2\hat{j} - \hat{k} \), \( \vec{\beta} = 2\hat{i} - \hat{j} + 3\hat{k} \) and \( \vec{\gamma} = 2\hat{i} + \hat{j} + 6\hat{k} \) be three vectors. If \( \vec{\alpha} \) and \( \vec{\beta} \) are both perpendicular to the vector \( \vec{\delta} \) and \( \vec{\delta} \cdot \vec{\gamma} = 10 \), then what is the magnitude of \( \vec{\delta} \)?
A.
\( \sqrt{3} \) units
B.
\( 2\sqrt{3} \) units
C.
\( \frac{\sqrt{3}}{2} \) unit
D.
\( \frac{1}{\sqrt{3}} \) unit
ANSWER :
B. \( 2\sqrt{3} \) units
46.
If \( \hat{a} \) and \( \hat{b} \) are two unit vectors, then the vector \( (\hat{a} + \hat{b}) \times (\hat{a} \times \hat{b}) \) is parallel to
A.
\( (\hat{a} - \hat{b}) \)
B.
\( (\hat{a} + \hat{b}) \)
C.
\( (2\hat{a} - \hat{b}) \)
D.
\( (2\hat{a} + \hat{b}) \)
ANSWER :
A. \( (\hat{a} - \hat{b}) \)
47.
A force \( \vec{F} = \hat{i} + 3\hat{j} + 2\hat{k} \) acts on a particle to displace it from the point \( A(\hat{i} + 2\hat{j} - 3\hat{k}) \) to the point \( B(3\hat{i} - \hat{j} + 5\hat{k}) \). The work done by the force will be
A.
5 units
B.
7 units
C.
9 units
D.
10 units
ANSWER :
C. 9 units
48.
For any vector \( \vec{a} \), \( |\vec{a} \times \hat{i}|^{2} + |\vec{a} \times \hat{j}|^{2} + |\vec{a} \times \hat{k}|^{2} \) is equal to
A.
\( |\vec{a}|^{2} \)
B.
\( 2|\vec{a}|^{2} \)
C.
\( 3|\vec{a}|^{2} \)
D.
\( 4|\vec{a}|^{2} \)
ANSWER :
B. \( 2|\vec{a}|^{2} \)
49.
A man running round a racecourse notes that the sum of the distances of two flag-posts from him is always 10 m and the distance between the flag-posts is 8 m. The area of the path he encloses is
A.
\( 18\pi \) square metres
B.
\( 15\pi \) square metres
C.
\( 12\pi \) square metres
D.
\( 8\pi \) square metres
ANSWER :
B. \( 15\pi \) square metres
50.
The distance of the point (1, 3) from the line \( 2x + 3y = 6 \), measured parallel to the line \( 4x + y = 4 \), is
A.
\( \frac{5}{\sqrt{13}} \) units
B.
\( \frac{3}{\sqrt{17}} \) unit
C.
\( \sqrt{17} \) units
D.
\( \frac{\sqrt{17}}{2} \) units
ANSWER :
D. \( \frac{\sqrt{17}}{2} \) units