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Water is filled in a flask up to a height of 20 cm. The bottom of the flask is circular with radius 10 cm. If the atmospheric pressure is $1.013 \times 10^5$ Pa,find total force exerted on the bottom of flask. Take g = 10 ms-2 and density of water = 1000 kgm-3. P0 is atmospheric pressure here.

Now, here if I draw the FBD of the base of flask. Then, there are three pressures acting on the base. Atmospheric pressure acting from top and below because fluids exerts pressure in all directions. Then is the hpg pressure.

Total pressure on the bottom of flask is $P_0 -P_0 + hpg$. Is this correct if it asked total pressure acting on the base? 

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From the inside of the flak the pressure is $P_0+ hg\rho$.

If you are looking for the force that secrets force on the base then that force is $(P_0+ hg\rho- P_0 )A$.

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  • $\begingroup$ So I am right what I wrote for the second equation in your answer if you compare with mine $\endgroup$
    – srijan Sri
    Jan 23 at 19:38
  • $\begingroup$ Your 1st equation is for force exerted by water on the base right $\endgroup$
    – srijan Sri
    Jan 23 at 19:38
  • $\begingroup$ the first equation describes the pressure on the inside of the flask $\endgroup$
    – NMech
    Jan 23 at 19:39
  • $\begingroup$ the second equation describes the force that you need to use when you are doing structural calculations. there is a subtle difference between them. In the first $P_0$ is included. In the second it isn't. $\endgroup$
    – NMech
    Jan 23 at 19:40
  • $\begingroup$ Does 2nd one mean the total force exerted on the base sir. Wanting to know if it means the same thing $\endgroup$
    – srijan Sri
    Jan 23 at 19:41

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