Course Content
Class 11 Physics Chapter 4 Motion In A Plane
4 Motion in a plane 4.1 Introduction 4.2 Scalars and vectors 4.3 Multiplication of vectors by real numbers 4.4 Addition and subtraction of vectors – graphical method 4.5 Resolution of vectors 4.6 Vector addition – analytical method 4.7 Motion in a plane 4.8 Motion in a plane with constant acceleration 4.9 Relative velocity in two dimensions 4.10 Projectile motion 4.11 Uniform circular motion
Class 11 Physics Chapter 5 Laws of motion
Section Name Topic Name 5 Laws of motion 5.1 Introduction 5.2 Aristotle’s fallacy 5.3 The law of inertia 5.4 Newton’s first law of motion 5.5 Newton’s second law of motion 5.6 Newton’s third law of motion 5.7 Conservation of momentum 5.8 Equilibrium of a particle 5.9 Common forces in mechanics 5.10 Circular motion 5.11 Solving problems in mechanics
Class 11 Physics Chapter 6 Work Energy and Power
Section Name Topic Name 6 Work Energy and power 6.1 Introduction 6.2 Notions of work and kinetic energy : The work-energy theorem 6.3 Work 6.4 Kinetic energy 6.5 Work done by a variable force 6.6 The work-energy theorem for a variable force 6.7 The concept of potential energy 6.8 The conservation of mechanical energy 6.9 The potential energy of a spring 6.10 Various forms of energy : the law of conservation of energy 6.11 Power 6.12 Collisions
Class 11 Physics Chapter 7 Rotation motion
Topics Introduction Centre of mass Motion of COM Linear Momentum of System of Particles Vector Product Angular velocity Torque & Angular Momentum Conservation of Angular Momentum Equilibrium of Rigid Body Centre of Gravity Moment of Inertia Theorem of perpendicular axis Theorem of parallel axis Moment of Inertia of Objects Kinematics of Rotational Motion about a Fixed Axis Dynamics of Rotational Motion about a Fixed Axis Angular Momentum In Case of Rotation about a Fixed Axis Rolling motion
Class 11 Physics Chapter 9 mechanics properties of solid
Section Name Topic Name 9 Mechanical Properties Of Solids 9.1 Introduction 9.2 Elastic behaviour of solids 9.3 Stress and strain 9.4 Hooke’s law 9.5 Stress-strain curve 9.6 Elastic moduli 9.7 Applications of elastic behaviour of materials
Class 11 Physics Chapter 11 Thermal Properties of matter
Section Name Topic Name 11 Thermal Properties of matter 11.1 Introduction 11.2 Temperature and heat 11.3 Measurement of temperature 11.4 Ideal-gas equation and absolute temperature 11.5 Thermal expansion 11.6 Specific heat capacity 11.7 Calorimetry 11.8 Change of state 11.9 Heat transfer 11.10 Newton’s law of cooling
Class 11 Physics Chapter 14 Oscillations
Section Name Topic Name 14 Oscillations 14.1 Introduction 14.2 Periodic and oscilatory motions 14.3 Simple harmonic motion 14.4 Simple harmonic motion and uniform circular motion 14.5 Velocity and acceleration in simple harmonic motion 14.6 Force law for simple harmonic motion 14.7 Energy in simple harmonic motion 14.8 Some systems executing Simple Harmonic Motion 14.9 Damped simple harmonic motion 14.10 Forced oscillations and resonance
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Law of Motion Class 11 Physics Notes and Solution

Balanced & Unbalanced forces

Balanced Forces:

  • Equal & Opposite forces
  • Do not cause any change in motion

Unbalanced Forces:

  • Unequal forces
  • Can be in the same or opposite direction
  • Causes a change in motion
Law of Motion Class 11 Physics Notes and Solution


Newton’s first law was for scenarios where net force = 0. The second law is for scenarios with net force not equal to 0. Momentum plays a crucial role in Second law.

  • Momentum is the product of mass of a body & its velocity
  • It is a Vector quantity
  • It is denoted by p = mv

For example, A ball of 1 kg moving with 10m/sec has a momentum 10kg m/sec.

Momentum of a system remains conserved. Therefore,

  • Greater force is required to set heavier bodies in motion
Law of Motion Class 11 Physics Notes and Solution

Newton’s Second Law

  • The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts.
  • Alternatively, the relationship between an object’s mass m, its acceleration a, and the applied force F is F = ma; the direction of the force vector is the same as the direction of acceleration vector.

F ∝ dp/dt  [Greater the change in momentum, greater is force]

F = k dp/dt

F = dp/ dt

F = d/ dt (mv)

Let, m: mass of the body be constant

F = m dv/dt

F = ma

  • Newton’s Second law is consistent with the First law

F = ma

If F =0, then a = 0

According to First law, if a = 0, Then F = 0

Thus, both the laws are in sync.

  • Vector form of Newton’s Second law
Law of Motion Class 11 Physics Notes and Solution


 m = 2 * 103

 u = 36 km/hr = 10m/s

 s = 50m

 v = 0

To find: a, F, t

Third equation of motion: v2 = u2 + 2as

0 = 100 + 2a * 50

Or,  a = -1 m/s2

Therefore, F = ma = (2 * 10) * 1 = 2 * 103 N

V = u + at

0 = 10 – t

 t = 10 sec

Problem 2: The only force acting on a 5kg object has components Fx = 15N and Fy = 25N. Find the acceleration of the object.


   m= 5kg

Fx = 15N, Fy = 25N

F = Fxi + Fyj

Law of Motion Class 11 Physics Notes and Solution
Law of Motion Class 11 Physics Notes and Solution
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