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hbk69
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Homework Statement
There are certain problems involving pressure where you are required to add the atmospheric pressure to solve the problems, i have done some problems where i work everything out but get the answer wrong because i did not add the atmospheric pressure. How can i overcome this problem? and how can i anticipate when i need to add the atmospheric pressure?, i will give some example questions where i made the mistake:
1)The depth of the ocean at a particular place is d=3.00km. The density of seawater Ps=1.03*10^3kgm^-3. What is the pressure P at the bottom of the ocean?
2)Two tubes are connected via a closed channel (forming an L-shaped figure). One tube is open-ended and has the length L1=100cm anthe other tube is close-ended and has the length L2=40cm. The L shaped structure is filled completely with water. What is the pressure at the top of the closed tube?
3) An ocean driver takes a deep breath at the surface, filling his lungs with air V=4L. The diver then descends to a depth of h=5m. The density of salt water=1030kgm^-3. The pressure of air at the surface is p=1.01x10^5 Pa. Assume that the body temperature T of the diver is the same at depth h as it is on the surface. Fine the volume of air in the lungs at this depth.
The Attempt at a Solution
In the questions above why was the atmospheric pressure added to each answer?
I calculated the answer for the questions above but failed to add the atmospheric pressure and although they stated the atmospheric pressure in each question (1.013*10^5 Pa) one would think that you'd automatically would know that you add it to your answer but what if that is not the case, i want to understand why we add the atmospheric pressure and how can i generally anticipate if i need to or not .
Thanks for any help or guidance