Hi, Just wondering if anyone has any thoughts on how to approach this question: A U-tube has vertical arms of radii 'r' and '2r', connected by a horizontal tube of length 'l' whose radius increases linearly from r to 2r. The U-tube contains liquid up to a height 'h' in each arm. The liquid is set oscillating, and at a given instant the liquid in the narrower arm is a distance 'y' above the equilibrium level. Show that the potential energy of the liquid is given by... U = (5/8)g(rho)(pi)(r^2)(y^2) 'y' is the change in height. Thanks!!