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Physics Notes Class 11 CHAPTER 4
MOTION IN A PLANE part 1
Those physical quantities which require magnitude as well as direction for their complete
representation and follows vector laws are called vectors.
Vector can be divided into two types
1. Polar Vectors
These are those vectors which have a starting point or a point of application as a displacement,
force etc.
2. Axial Vectors
These are those vectors which represent rotational effect and act along the axis of rotation in
accordance with right hand screw rule as angular velocity, torque, angular momentum etc.
Scalars
Those physical quantities which require only magnitude but no direction for their complete
representation, are called scalars.
Distance, speed, work, mass, density, etc are the examples of scalars. Scalars can be added,
subtracted, multiplied or divided by simple algebraic laws.
Tensors
Tensors are those physical quantities which have different values in different directions at the
same point.
Moment of inertia, radius of gyration, modulus of elasticity, pressure, stress, conductivity,
resistivity, refractive index, wave velocity and density, etc are the examples of tensors.
Magnitude of tensor is not unique.
Different Types of Vectors
(i) Equal Vectors Two vectors of equal magnitude, in same direction are called equal vectors.
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(ii) Negative Vectors Two vectors of equal magnitude but in opposite directions are called
negative vectors.
(iii) Zero Vector or Null Vector A vector whose magnitude is zero is known as a zero or null
vector. Its direction is not defined. It is denoted by 0.
Velocity of a stationary object, acceleration of an object moving with uniform velocity and
resultant of two equal and opposite vectors are the examples of null vector.
(iv) Unit Vector A vector having unit magnitude is called a unit vector.
A unit vector in the direction of vector A is given by
Â=A/A
A unit vector is unitless and dimensionless vector and represents direction only.
(v) Orthogonal Unit Vectors The unit vectors along the direction of orthogonal axis, i.e., X –
axis, Y – axis and Z – axis are called orthogonal unit vectors. They are represented
by
(vi) Co-initial Vectors Vectors having a common initial point, are called co-initial vectors.
(vii) Collinear Vectors Vectors having equal or unequal magnitudes but acting along the same
or Ab parallel lines are called collinear vectors.
(viii) Coplanar Vectors Vectors acting in the same plane are called coplanar vectors.
Physics Notes Class 11 CHAPTER 4
MOTION IN A PLANE part 1
Those physical quantities which require magnitude as well as direction for their complete
representation and follows vector laws are called vectors.
Vector can be divided into two types
1. Polar Vectors
These are those vectors which have a starting point or a point of application as a displacement,
force etc.
2. Axial Vectors
These are those vectors which represent rotational effect and act along the axis of rotation in
accordance with right hand screw rule as angular velocity, torque, angular momentum etc.
Scalars
Those physical quantities which require only magnitude but no direction for their complete
representation, are called scalars.
Distance, speed, work, mass, density, etc are the examples of scalars. Scalars can be added,
subtracted, multiplied or divided by simple algebraic laws.
Tensors
Tensors are those physical quantities which have different values in different directions at the
same point.
Moment of inertia, radius of gyration, modulus of elasticity, pressure, stress, conductivity,
resistivity, refractive index, wave velocity and density, etc are the examples of tensors.
Magnitude of tensor is not unique.
Different Types of Vectors
(i) Equal Vectors Two vectors of equal magnitude, in same direction are called equal vectors.
, 2|Page
(ii) Negative Vectors Two vectors of equal magnitude but in opposite directions are called
negative vectors.
(iii) Zero Vector or Null Vector A vector whose magnitude is zero is known as a zero or null
vector. Its direction is not defined. It is denoted by 0.
Velocity of a stationary object, acceleration of an object moving with uniform velocity and
resultant of two equal and opposite vectors are the examples of null vector.
(iv) Unit Vector A vector having unit magnitude is called a unit vector.
A unit vector in the direction of vector A is given by
Â=A/A
A unit vector is unitless and dimensionless vector and represents direction only.
(v) Orthogonal Unit Vectors The unit vectors along the direction of orthogonal axis, i.e., X –
axis, Y – axis and Z – axis are called orthogonal unit vectors. They are represented
by
(vi) Co-initial Vectors Vectors having a common initial point, are called co-initial vectors.
(vii) Collinear Vectors Vectors having equal or unequal magnitudes but acting along the same
or Ab parallel lines are called collinear vectors.
(viii) Coplanar Vectors Vectors acting in the same plane are called coplanar vectors.
