Sandeepan Dhar Choudhary asked:
“When the ball falls on the earth, the earth also moves up to meet it. But the motion of the earth is not noticeable. Explain why?”
The force exerted by the ball on earth is same as the force exerted by the earth on the ball. The acceleration of the ball towards earth is approximately 10 m/s2.
The acceleration of earth towards the ball = force/mass of earth ≈ 10-23 m/s2
When the earth moves towards the ball with this acceleration, the time required to travel the distance will be very large. If we assume a distance of 1m, and from the equation
we get t ≈ 1012 seconds whereas the ball reaches the earth in 0.4 seconds
[warning]In a nut shell, we can say that we cannot notice the motion of earth towards the ball due to the extremely low value of acceleration of earth towards the ball.[/warning]