Galileo sometimes used his pulse to time motions. what was the timing problem that galileo encountered? (drop a rubber ball from a height of about 2 m and try to determine how many pulse beats elapsed before it hits the ground.)

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?