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## Homework Statement

the spring of the pressure gauge. has a force constant of 1250 N/m, and the piston has a diameter of .012m. As the gauge is lowered into water in a lake, what change in depth causes the piston to move by .0075 m

## Homework Equations

P= P[itex]_{0}[/itex] + [itex]\rho[/itex]gh variation with pressure

P=F/A

## The Attempt at a Solution

I did this problem including P[itex]_{0}[/itex] (atmospheric pressure) and it was wrong, then did it without atmospheric pressure and got it right. I am confused as to why atmospheric pressure is not included. because Isn't the pressure at P at a depth H below a point in the liquid at which pressure is P[itex]_{0}[/itex] by an ammount [itex]\rho[/itex]gh?