In a mercury-in-a-glass thermometer, it is observed that the mercury level drops first before it rises. How come this happens?

If the force applied to an object remains constant, is more power needed for the object to move faster ? explain

A2k pendulum has a speed of 1 m/s at a height of 1/2 meter

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?