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
Class 11th Physics Online Class For 100% Result
About Lesson

Introduction ( Class 11 Physics Gravitation )

  • Whenever we throw an object towards the sky it will fall back onto the ground.
  • For Example: – A ball comes down when thrown up. Rain drops fall towards the ground; Planets revolve in an elliptical orbit around sunetc.
Class 11 Physics Gravitation

Planets revolving in the elliptical orbit.

Class 11 Physics Gravitation
Class 11 Physics Gravitation

Leaves fall off the tree.

  • There is a force due to which all things are attracted towards the earth. This force is known as Gravitation.
  • Gravitation is the force of attractionbetween all masses in the universe, especially the force of attraction exerted by the earth on all the bodies near its surface.
  • In this chapter we will take a look at gravitation force, its laws, and we will also study about the planetary motion.

Gravitational Constant

Newton’s view of Gravitation

  • Newtonwas the first scientist who studied the force of gravitation.
  • According to him there is a force which is exerted by the surface of the earth because of which all the objects are attracted towards the surface of the earth.
  • He also concluded that all objects in this universe attract each other with a force. This force is Gravitation force.
Class 11 Physics Gravitation
Class 11 Physics Gravitation
  • F ∝ m1m2
  • Force is ∝to the product of masses of 2 bodies.
  • F ∝ 1/r2
  • Force is inversely proportional to the square of the distance between the 2 bodies. 
  • Combining above equations:-
  • F ∝ m1m2/r2
  • F= G m1m2/r2

Where G = universal Gravitational constant.

  • Its value is constant and it never changes.
  • m1 and m2are masses of 2 bodies.
  • r = distance between the bodies.

Gravitational Constant: Cavendish experiment

  • Cavendish performed an experiment to calculate the value of G.
  • To calculate the value of G he took a wooden plank and attached two 2 balls on either side of the plank and hung this with a thin thread from the top.
  • He introduced 2 very big balls and those balls are near the smaller balls.
  • He observed that the small balls got attracted to big balls and wooden plank started rotating and as a result the thin thread started twisting.
  • This happened because of force of attraction between the small balls and bigger balls.
  • He observed that :-
  1. Plank rotates till twisting force becomes equal to the gravitational force between the balls.

𝛕 = G m1m2/r2

LƟ = G m1m2/r2

  • By using the above equation he calculated the value of G,
  • G= 6.67×10-11Nm2/kg2                        
  • Units of G : Nm2/kg2
Class 11 Physics Gravitation
Class 11 Physics Gravitation

Problem:- Calculate the gravitational force of attraction between 2 lead balls of mass 20kg and 10kg separated by a distance of 10cm?

Answer: m1= 20kg , m2=10kg , r=10cm = 10/100 = 0.1m


F=G m1m2/r2

= 6.67×10-11x 20×10 / (0.1)2

F = 1.3 x 10-6N

Acceleration due to gravity of the earth

  • Acceleration attained due to gravity of earth.
  • All the objects fall towards the earth because of gravitational pull of the earth.
  • And when abody is falling freely, it will have some velocity and therefore it will attain some acceleration. This acceleration is known as acceleration due to gravity.
  • It is a vector quantity.
  • Denoted by ‘g’.
  • Its value is 9.8m/s2.

Example:-Stones falling from a rock will have some velocity because of which some acceleration. This acceleration is due to the force exerted by the earth on the rocks.This is known as acceleration due to gravity.

Class 11 Physics Gravitation
Class 11 Physics Gravitation
Join the conversation
Wisdom TechSavvy Academy