what would happen if gravitational force of the sum suddenly vanishes
Answers
What would happen if the gravity of the Sun instantly disappeared?
Right now the Sun's gravity pulls on the planets, just as Earth's gravity pulls down anything that is not held up by some other force and keeps you and me on the ground. Now the gravitational pull of the sun is only 0.0006 of the strength of the earth's gravity on the surface of the earth. But that's enough to pull the entire planet around in a big, nearly circular orbit, once per year.
So let’s just assume the Sun did not have gravity:
Now let’s first understand gravity and how it works. If the Sun is pulling the planets with gravity, why don't they just fall in and burn up? Well, in addition to falling toward the Sun, the planets are moving sideways. This is the same as if you have a weight on the end of a string. If you swing it around, you are constantly pulling it toward your hand, just as the gravity of the Sun pulls the planet in, but the motion sideways keeps the ball swinging around. Without that sideways motion (gravity), it would fall to the center; and without the pull toward the center, it would go flying off in a straight line, which is, of course, exactly what happens if you let go of the string.