Hi all, I am quite confused by the forces relating to a horizontlly placed spring when someone directly exerts a force to the compress it. If I exert a force F to the right to compress the spring, which, say, is placed against a wall, the spring exerts an elastic force on me but I don't see how these two forces are related because they are exerted on different bodies. How can they be balanced out if they act on different bodies? Let me thank you in advance. I have been bothered by this problem for a while.