

The vector OP
represents the displacement of 40 km, 30
o
east of north.
2. Classify the following measures as scalars and vectors.
(i) 10 kg (ii) 2 metres north-west (iii) 40°
(iv) 40 watt (v) 10
–19
coulomb (vi) 20 m/s
2
Solution:
(i)
10 kg is a scalar quantity because it has only magnitude.
(ii)
2 meters north-west is a vector quantity as it has both magnitude and direction.
(iii)
40° is a scalar quantity as it has only magnitude.
(iv)
40 watt is a scalar quantity as it has only magnitude.
(v)
10
–19
coulomb is a scalar quantity as it has only magnitude.
(vi)
20 m/s
2
is a vector quantity as it has both magnitude and direction.
3. Classify the following as scalar and vector quantities.
(i) time period (ii) distance (iii) force
(iv) velocity (v) work done
Solution:
(i)
Time period is a scalar quantity as it has only magnitude.
(ii)
Distance is a scalar quantity as it has only magnitude.
(iii)
Force is a vector quantity as it has both magnitude and direction.
(iv)
Velocity is a vector quantity as it has both magnitude as well as direction.
(v)
Work done is a scalar quantity as it has only magnitude.
4. In Figure, identify the following vectors.
(i) Coinitial (ii) Equal (iii) Collinear but not equal
Solution:
directions are not the same.
Exercise 10.2 Page No: 440
1. Compute the magnitude of the following vectors.
Solution:
Given, vectors are
2. Write two different vectors having the same magnitude.
Solution:
3. Write two different vectors having the same direction.
Solution:
Two different vectors having the same directions are
Let us
4. Find the values of
x
and
y
so that the vectors
6. Find the sum of the vectors.
Solution:
Let us find the sum of the vectors.
7. Find the unit vector in the direction of the vector.
Solution:
We know that
8. Find the unit vector in the direction of vector, where P and Q are the points
(1, 2, 3) and (4, 5, 6), respectively.
Solution:
We know that,
Solution:
We know that,
Solution:
Firstly,
Solution:
First,
Therefore, we can say that the given vectors are collinear.
Solution:
First,
13. Find the direction cosines of the vector joining the points A (1, 2, –3) and
B (–1, –2, 1) directed from A to B.
Solution:
We know that the given points are A (1, 2, –3) and B (–1, –2, 1).
Now,
Solution:
Firstly,
16. Find the position vector of the midpoint of the vector joining the points P (2, 3, 4) and Q (4, 1, – 2).
Solution:
The position vector of mid-point R of the vector joining points P (2, 3, 4) and Q (4, 1, – 2) is given by
Solution:
We know
Given position vectors of points A, B, and C are
Hence, proved that the given points form the vertices of a right-angled triangle.
18. In triangle ABC (Fig 10.18), which of the following is not true.
Solution:
First, let us consider,
Exercise 10.3 Page No: 447
Solution:
First, let us consider,
2. Find the angle between the vectors
Hence, the angle between the vectors is cos
-1
(5/7).
Solution:
First,
Solution:
First,
Hence, the projection is 60/
√
114.
5. Show that each of the given three vectors is a unit vector.
Also, show that they are mutually perpendicular to each other.
Solution:
It is given that
6. Find
Solution:
Let us consider,
7. Evaluate the product
8. Find the magnitude of two vectors
Hence, the magnitude of the two vectors is 1.
Solution:
Let us consider,
Hence, the value is
√
13.
Solution:
We know that the
Solution:
Let us consider,
Solution:
Consider the given vectors,
Hence, the value is -3/2.
Solution:
First,
Solution:
We know,
Hence, the angle is cos
-1
(10/
√
102).
16. Show that the points A (1, 2, 7), B (2, 6, 3) and C (3, 10, –1) are collinear.
Solution:
Let us consider,
Given points are A (1, 2, 7), B (2, 6, 3), and C (3, 10, –1).
Now,
Therefore, the given points A, B, and C are collinear.
Solution:
First, consider
Solution:
Explanation:
10.1 Introduction
10.2 Basic Concepts
10.3 Types of Vectors
10.4 Addition of Vectors
10.5 Multiplication of a Vector by a Scalar
10.5.1 Components of a vector
10.5.2 Vector joining two points
10.5.3 Section formula
10.6 Product of Two Vectors
10.6.1 Scalar (or dot) product of two vectors
10.6.2 Projection of a vector on a line
10.6.3 Vector (or cross) product of two vectors
