What Is Gravitation?
We thought
that Gravitation is a Phenomenon of
attraction between any two objects in the universe. The objects may be
terrestrial or celestial. Further, the objects may be of any size, shape or
mass and they may be any distance apart, with any medium between them.
But
when I wrote this statement many question arised in your mind such that why we
humans do not have gravitational force? why we not attract towards each other?
Before we discusse you have to know some more points about gravitation.
We
observed that when a body is droped from a certain height, it falls towards the
Earth. The motion in the body must have been initiated by a force exeted by the
Earth on the body.
All planets move around the sun in a circular orbits, wherein
their direction of the motion changes continuously the change in direction must
be due to an unbalanced force on each planet exert by sun.
Similarly the moon revolves around the sun in a circular orbit
the direction of the motion of moon changes continuously this must be due to an
invalid force on moon exerts by Earth.
Newton grapes that the
nature of the force involved in all the three cases must be same Newton called
this force as the gravitational force.
Now A final topic that is what is
Gravitation starts.
Newton was sitting under an apple tree when an apple fell on
him he thought that the Apple fell due to the downward pole of Earth on Apple
however it was not fully this idea was given by his friend who was also a
scientist.
When a body is thrown up it reaches a certain height and then
fell down. The continuous downward pull off the Earth on the body decrease its
velocity in upward direction to zero at some height. The body cannot rise
further. This is, therefore, the maximum height.
Consider a piece of stone tied to one end of the string. Hold
the other end of the string in hand and whirl it around with a constant speed.
Stone moving in a circular path with a certain speed but its
direction of motion changes continuously the change in direction. of the motion
involved the change in the velocity or acceleration of the stone. The external
force F that causes the acceleration and keep the stone moving uniformly along
a circular path is acting towards the centre of the circular path this is
called centripetal force. that means, Centre seeking force. At any instant, if
we release the string, the stone files along a Tangent to the circular path at
the instant this is because the movement the string released centripetal force
is no longer provided the stone is free to fly off along the tangent.
Based on this activity we can perceive that the motion of the Moon
around the sun is due to the centripetal force provided by the force of
attraction of the Earth on the moon. Similarly, is all the Planet of our solar
system revolves around the sun centripetal force must be acting on each planet
providing the force of attraction of the sun on the planet.
From this observation Newton concludes that it is not only the
Earth which attracts an apple and the moon. And it is not only the sun which
attract every planet. Rather every object in this universe attract every other
object this force of attraction is called gravitational force and this
phenomena is called Gravitation. We, therefore, define:
Gravitation as the phenomena of attraction between any two objects
in this universe. The object may be Terrestrial or celestial. Further, the
object may be of any size shape or mass and they may be at any distance apart
with any medium between them.
Note that force of
gravitation is always the force of attraction. It is never repulsive; the
gravitational force of attraction between any two objects is always mutual. It
means if the Earth attracts an apple, the apple also attracts the Earth towards
it with an equal force.
NEWTON'S UNIVERSAL LAW OF GRAVITATION
Every object in the
Universe attracts every other object with a force which is (i) directly
proportional to the product of their masses, and (ii) inversely proportional to
the square of the distance between their centres. The direction of the force is
along the line joining the centres of two objects.
Consider two objects A and B of masses m1 and m2,
respectively. Let r be the distance between their centre, If F is the
gravitational force of attraction between these objects, then according to
Newton's law of gravitation, the force between two objects is directly
proportional to the product of their masses, i.e.,
And the force between two objects is inversely proportional to
the square of the distance between their centres, i.e.,
By both
F=Gm1 m2/r2
Where G is a constant of proportionality and is called
universal gravitational constant.
Eqn, (4) is the mathematical expression of Newton's universal
law of gravitation. The formula reveals that when my, my are large, F is large,
i.e., the gravitational force of attraction between heavier bodies is larger
than that between lighter bodies. Further, if we double the distance between
two bodies, the gravitational force of attraction between them becomes
one-fourth. And if the distance between two bodies is halved, the gravitational
force of attraction between them becomes four times.
Newton's law of gravitation is called universal law of
gravitation because it is applicable to all the bodies having mass. These
bodies may be terrestrial (which are on Earth) or celestial (which are in outer
space such as stars, planets, satellites etc.). Further, the bodies may be of
any shape, size or mass and they may be any distance apart (small or big) with
any medium between them.
So, these are my views on Gravitation Please write down your
views on Gravitation.
And also write which topic you like next by the way I have
final some topic which I upload soon so stay tuned.
Thank You!
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