Question

Newton's law of universal gravitation states that a particle attracts every other particle in the universe with a force.
Does that mean when an apple falls on the earth due to gravitational attraction, the earth moves towards the apple too?

• A. Yes
• B. No
• C. Only if the apple has a mass less than 500 grams
• D. Only if the apple is massless

Answer 1

The correct option is A Yes

Force of gravity between two bodies is given by the formula $F=\frac{GMm}{r^2}$
The magnitude of force F will be the same for both objects, only in opposite directions.
We know F = ma, so as the force acting on both the Earth and the apple are same, they must have differing accelerations as the mass of both the substances are different.
Mass of Earth (M) is $6\times {10}^{24}kg$ and the mass of an apple (m) is approximately 0.1 kg. Since M >>> m the acceleration of the Earth is almost negligible as compared to the apple, we usually tend to ignore it.