L1 - Gravitational Force, Class 9, Science Video Lecture

gravitational force in a moment of
inspiration Sir Isaac Newton watched an
Apple fall to the ground and discovered
the principle of gravity gravity is the
force of attraction by which earth
attracts everything towards its center
if so why does the moon revolve around
the earth Newton argued that at each
point of its orbit the moon Falls
towards the Earth instead of going off
in a straight line this is due to
centripetal force a continuously moving
body in a circular path will change its
velocity to accelerate itself the force
that causes this acceleration and keeps
the body moving along the circular path
towards the center is called centripetal
force the motion of the Moon around the
earth is due to the centripetal force
the centripetal force is provided by the
gravitational force of attraction of the
earth if there was no such force the
moon would pursue a uniform
straight-line motion towards the earth
all objects in the universe attract each
other this force of attraction between
objects is called the gravitational
force every object in the universe
attracts each other with a force which
is proportional to the product of their
masses and inversely proportional to the
square of the distance between them
consider two objects a and B and their
respective masses as Capital m and small
M they lie at a distance D according to
the law gravitational force F is
directly proportional to the product of
the masses of two objects a and B a and
F are inversely proportional to the
square root of the distance between the
two objects F is equal to G into M M by
D Square where Jesus gravitational
constant and the value of G is equal to
six point six seven three into ten to
the power of minus 11 Newton meter
square per kg square
origin of the law of gravitation in the
16th century Copernicus proposed a
heliocentric that is the Sun centric
scheme in which the earth and the
planets moved about the Sun during the
17th century Johannes Kepler proposed
three laws that describe the motion of
planets the first one is the law of
orbit all planets move in ellipses
orbits having the Sun at one focus the
second the law of areas align joining
any planet to the Sun sweeps out equal
areas in equal times to explain that
consider two points a and B on the
planet's orbit now as planet moves from
point A to point B the area such covered
is in T seconds now between the point C
and D the planet will cover the same
area in T seconds the area between a and
B and the area between C and D is equal
the third is the law of periods the
square of the period of any planet about
the Sun is proportional to the cube of
the semi-major axis of its orbit the
length of the major axis is 2a the
distance between the point of
intersection of semi-major axis on major
axis to the orbit is a now according to
the law of period t-square is directly
proportional to a cube things to
remember the force of attraction between
objects is known as gravitational force
according to the law of gravitation F is
equal to G into mm by d square the force
that causes a moving body to accelerate
and move along a circular path towards
its center is called centripetal force
due to the centripetal force the moon
revolves around the earth in the 16th
century Copernicus proposed a
heliocentric or sun-centered universe
Johannes Kepler proposed three laws that
describe the motion of planets that is
law of orbit law of areas and law of
periods
you