Question

A simple pressure gauge comprises an evacuated cylindrical piston with a spring inside (see figure below or on page 400 of the book). The spring obeys Hooke’s law and the spring constant is 1250 N/m. The piston has a diameter of 1.20 cm. The piston is lowered into a lake. Before lowering the piston into the water (ρ = 1.00 x 10³ kg/m³) the spring was at its equilibrium length. Calculate how deep the piston should go to cause the piston to move in by 0.750 cm ?

Answer 1