INTRODUCTION
The motion of celestial bodies such as the sun, the moon, the earth and the planets etc.
has been a subject of fascination since time immemorial. Indian astronomers of the
ancient times have done brilliant work in this field, the most notable among them being
Arya Bhatt the first person to assert that all planets including the earth revolve round the
sun.
According to this law "Each particle attracts every other particle. The force of attraction between
them is directly proportional to the product of their masses and inversely proportional to square of
the distance between them
The force exerted by a particle on other particle remains unaffected by the presence
of other nearby particles in space
The space surrounding the body within which its gravitational force of attraction is experienced
by other bodies is called gravitational field. Gravitational field is very similar to electric field in
electrostatics where charge 'q' is replaced by mass 'm' and electric constant 'K' is replaced by
gravitational constant 'G'. The intensity of gravitational field at a point is defined as the force
experienced by a unit mass placed at that point
The gravitational potential at a point in the gravitational field of a body is defined as the amount of work
done by an external agent in bringing a body of unit mass from infinity to that point, slowly (no change in
kinetic energy).
The work done by an external agent to move unit mass from
a point to another point in the direction of the field E,
GRAVITATIONAL POTENTIAL & FIELD FOR DIFFERENT OBJECTS
Point P outside the shell
GRAVITATIONAL POTENTIAL ENERGY
The gravitational self-energy of a body (or a system of particles) is defined as the work done
by an external agent in assembling the body (or system of particles) from infinitesimal
elements (or particles) that are initially an infinite distance apart.
It is the acceleration, a freely falling body near the earth’s surface acquires due to the
earth’s gravitational pull. The property by virtue of which a body experiences or exerts a
gravitational pull on another body is called gravitational mass mG, and the property by
virtue of which a body opposes any change in its state of rest or uniform motion is called its
VARIATION OF ACCELERATION DUE TO GRAVITY
IMPORTANT POINTS
The minimum speed required to send a body out of the gravity field of a planet (send it to )
Suppose a planet is revolving around the sun, or a satellite is revolving around the earth, then the planetary
motion can be studied with help of Kepler’s three laws
Suppose a planet is revolving around the sun in circular orbit
CIRCULAR MOTION OF A SATELLITE AROUND A PLANET
Total energy of the satellite moving in circular orbit
We know that the earth rotates about its axis with
angular velocity
PATH OF A SATELLITE ACCORDING TO DIFFERENT SPEED OF PROJECTION
