The horizontal surface on which the objects slide is frictionless. The acceleration of gravity is 9.8 m/s2. block 1 is 1kg block 2 is 9kg block 3 is 4kg from left to right. If Fl = 20 N and Fr = 7 N, what is the magnitude of the force exerted on the block with mass 9 kg by the block with mass 4 kg? Answer in units of N.

Why does the equilibrium position of the spring change when a mass is added to the spring? will the mass oscillate around the new equilibrium position of the spring or the previous position without a mass attached to the spring? if the equilibrium position of the spring changes by 20 cm (assuming no initial mass) when a mass is added to the spring with constant 4.9 kg/s^2, what is the mass of the object attached to the spring?