basic forces question about the reaction force

Question

For a object like this, is the upward force applied of 2000N counted as part of the total reaction force to gravity? or is it separate and therefore the object will motion upwards.

Answer 1

$R$ is not a reaction to gravity, it is a force that is necessary to keep the object on a surface. $R$ is a reaction to the force with which the object pushes on the surface. What it means that the sum of the forces in the vertical direction is zero. You can get this from second principle and superposition principle (sum of the forces equals to mass times acceleration, and you say that the acceleration in the vertical direction is zero). You have $R$ and $2000N$ acting up, and $mg=700\cdot 10N=7000N$ acting down. $$R+2000N=7000N\\R=5000N$$ The action-reaction pair that corresponds to $700g$ is the force (at the center of the Earth) with which the Earth is attracted to the object (also 700g).