This document outlines key concepts related to gravitation and Newton's laws of motion. It discusses Isaac Newton and his formulation of the universal law of gravitation. Some main points covered include Newton's three laws of motion, gravitational force, weight, escape velocity, Kepler's laws of planetary motion, and applications of gravitation such as keeping objects on Earth and influencing tides. The document provides an overview of fundamental principles in classical mechanics developed by Newton to describe motion and gravitational attraction.

2. Plan 0f talk
• Gravitation
• Isaac Newton
• The universal law of gravitation
• Newton’s First law
• Newton’s second law
• Newton’s third law
• Weight and Gravitational Potential Energy
• Escape velocity
• Motion of planets
• Kepler’s Laws of Planetary Motion
• Uses of Gravitation

3. Gravitation
The force of attraction by
the earth on bodies is
called gravitation.

4. Isaac Newton
• Sir Isaac Newton
(1643- 1726) was an
English mathematician,
physicist and scientist.
He is widely regarded as
one of the most influential
scientists of all time, developing new laws of
mechanics, gravity and laws of motion.

5. Newton?

6. THE UNIVERSAL LAW OF
GRAVITATION
• Every particle of matter in the universe attracts every
other particle with a force that is directly proportional
to the product of the masses of the particles and
inversely proportional to the square of the distance
between them.
• Any two point particles with masses m1 and m2
attract each other by a force whose magnitude is
directly proportional to the product of the two
masses, that is m1m2 and inversely proportional to
the square of the distance R between them. The
direction of the force is along the line joining the two
masses.

7. In the mathematical form the law can be represented
as…

8. Newton’s First law
• A body cannot change its state of rest or that
of uniform motion along a straight line ,
unless an external force acts on it.
• According to this law ,the net external force
on a body is zero, its acceleration is zero. A
body will have acceleration only if there is a
net external force on it.

9. Newton’s second law
• The rate of change of momentum of a body is
directly proportional to the force acting on it
and takes place in the direction of the force.
• Newton’s second law written in the form
F=ma

10. Newton’s third law
• For every action, there is an equal and
opposite reaction.
• According to this law ,if a body A exerts a
certain force (action)on another body B , then
B would exert on A an equal force(reaction)
in the opposite direction.

11. Weight and Gravitational Potential
Energy
• The force exerted by the earth on a particle of mass
m by its weight
w=mg
where , g the gravitational acceleration due to the earth.
• we can now easily evaluate this quantity by equating the
weight with the gravitational force exerted by the earth at its
surface. That is,

12. • More generally for any two masses m1 and
m2 separated by centre-to-centre distance r :

13. Escape velocity
• The minimum speed with which a body must be projected
from the earth’s surface so that it completely overcomes the
gravitational pull of the earth and does not return to earth’s
surface is known as escape velocity.

14. Motion of planets
Planets are the non-luminous celestial
bodies revolving around the sun. The planets
in the increasing order of the distance from
the sun. The planets vary in
size,mass,temperature,atmospere
etc…….The observed motion of the planets
are described using the Kepler’s laws.

15. Kepler’s Laws of Planetary Motion
• Kepler’s First Law
All planets move around the sun in
elliptical paths with the sun at one
focus of the ellipse.
F1 F2
Sun
Planet
P

16. Kepler’s Second
Law
An imaginary line drawn from the sun to
the planet sweep out equal areas in equal
intervals of time.
Sun C
D
A
B

17. Kepler’s Third Law
The square of the period of
revolution of the planet around the
sun is proportional to the cube of
its mean distance from the sun.

18. Uses of Gravitation
1)It is the gravitational
force that keep
everything at its
place. Otherwise
we would have
been floating in the air.
Weightlessness in space vehicle
It is due to gravitation that we are walking on the Earth.

19. 2)It also keeps the
earth, sun and
other celestial
bodies at their
right places

20. 3)It is responsible for many natural
phenomenon on the earths like tides and
orbiting of moon around the earth.