Gravity
when an object is thrown up, it reaches a certain height and then falls to the earth. We are all familiar with these natural phenomena such as rainfall, snowfall, falling off an apple from a tree, etc.
The reason behind all these actions is gravity." Gravity is the force of attraction which is exerted by any planet towards its center on a body near its surface".
Earth attracts the moon towards its center with the force of gravity. In the same way, the moon also attracts the earth with a force of the same magnitude.
The force with which the objects attract each other is called the force of gravitation.
The mass of the earth is larger than that of the moon. That is why the moon orbits the earth.
Now, what is the range of Earth's gravity? How far Earth's gravity can be experienced by a body?
Suppose if we are in a stationary Space Station 400 km above the earth. We Would Still experience 90% of the gravity there that we experience on the ground. The Moon's surface is around 400,000 km away. Earth's gravitational pull will be less than 0.03 % of what we feel on the earth. If the distance increases, the gravitational pull will be continued to decrease but never dropped to zero.
orbital motion
whenever an object is moving forward and at the same time is pulled by gravity towards another object.
"The moon is not staying at one place, but it is orbiting around the earth.
Depth of Orbital motion
let us consider an example A ball is thrown in a horizontal direction with some velocity, and it travels a parabolic path due to continuous action of gravity. If we increase its velocity and then a long parabolic path is covered. But if we increase height (position of the throw) and its velocity, it becomes elliptical (nearly circular). The fact is that Earth is not flat; in fact, it is elliptical in shape.
The curvature of the downward bent trajectory would become equal to the curvature of the earth.
Back to the moon
The same process is done in the case of the moon. The moon has its own velocity, and a force of attraction exists between the Earth, and the Moon called gravitational force. The gravitational force provides the centripetal force to the Moon. This force keeps the moon moving along a circular path towards the center of the circular path.
If there were no such force, the moon would pursue a uniform, straight-line motion.
more clear from the example :
Tie a small piece of stone with thread. Hold the one end of the thread in your hand and whirl it around. Now release this thread. The force that keeps the object moving along the circular path acts towards the center, called centripetal force. In the absence of this force, the stone will be seen flying off along a straight line.
The balance between fall and escape
The mix of velocity and distance between earth and Moon always keeps them in a balancing situation. The change in velocity and distance may cause the escape or fall of the Moon.
If the moon were moving a lot faster, it would escape earth's gravity and fly off into space. If the moon were moving more slowly, then gravity would pull it down to the earth.
At every point of its orbit around the earth, the moon falls towards the earth instead of going off in a straight. But every time, it missed the surface of the earth. The motion is fast enough for it to fall around the earth rather than into it.
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