Question

2. An automated "diving machine is used to retrieve underwater treasure. The machine is comprised of a very long evacuated metal cylinder fitted with a moveable piston that is sealed to keep water out. See figure below. The cylinder has a diameter of 1 em, and rests in a horizontal position at the surface of the ocean. When the piston is pushed all the way in, to the end of the cylinder the underwater weight is 100 N and the cylinder sinks to the bottom of the sea, which is at a depth of 100 m. At this point an artifact with underwater weight 50 N is attached to the cylinder. The piston is then withdrawn, until the cylinder, together with the treasure, floats to the surface. (a) How much force in N) must be applied to withdraw the piston ata depth of 100 m How much work (in Joules) must be performed to withdraw the piston to the point where the cylinder, together with treasure, will just barely float? How much (negative) work must be performed to push the pistorn back in once the cylinder is at the surface in order to prepare the cylinder for the next dive? What is the net work for a dive-cycle? (b) What is the change in potential energy of the cylinder & treasure, irn moving from a depth of 100 m up to the surface? How does this compare with the net work in part (a)?

Answer 1

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