They are asking for the force (weight) on the Earth due to the presence of the apple. It is also 1 N, but in the opposite direction (towards the apple).
This follows from Newton's third law of motion, but can also be derived from his law of gravity.
The weight of an apple near the surface of the earth is 1N. What is the weight of Earth in the gravitational field of the apple?
2 answers
1N
7 answers