According to the third law of motion when a body exerts a force on another body then the other body also exerts force and both are equal and opposite. So when earth exerts a force on a falling apple then the force of the same magnitude should be exerted by the apple also towards earth. So why don't the earth moves towards the apple as force is equal?

If we assume an apple has a mass of 100 gm or 0.1 kg. Its weight F = ma = 0.1 $ \times $ 9.8 = 0.98 Newtons is the force with which Earth attracts that apple.

Using Newton's third law of motion, we can conclude that the force exerted on the earth is 0.98 Newtons towards the apple. The apple exerts the same force on the earth as the earth exerts on the apple. However, the earth weighs about 6′000′000′000′000′000′000′000′000 kilograms or $6 \times 10^{24}$ Kg as compared to 0.1 kg of apple. Apple moves towards Earth and Earth moves towards apple in the ratio of their masses. So the movement of Earth towards the apple is negligible and not apparent while the movement of the apple towards earth is easily detectable and visible.

The apple exerts exactly as much force on the Earth as the Earth exerts on it.

To the second point, the Earth is attracted to the apple. It only seems like it doesn't. This illusion is due to the fact that Earth is so much more massive than the apple.


Simply Easy Learning

Updated on: 10-Oct-2022


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