A U-tube open at both ends to atmospheric pressure is filled with an incompressible fluid of density . The cross-sectional area of the tube is uniform and the total length of the column of fluid is . A piston is used to depress the height of the liquid column on one side by a distance , and then is quickly removed. What is the frequency of the ensuing simple harmonic motion? Assume streamline flow and no drag at the walls of the U-tube. (Hint: use conservation of energy). Express your answer in terms of and acceleration due to gravity (enter L for and g for ).