A storage tank of negligible mass and 30m high is filled with gasoline. Please calculate the following. Use density values found in the book.

a) The gauge pressure and absolute pressure at the bottom of the tank.
b) The force that acts on a square access hatch at the bottom of the tank that measures 0.5m x 0.5m.
c) Given that the tank is shaped like a right circular cylinder with a height of 30 m and with a
base radius of 10m. The tank is attached to a
steel cable of negligible mass and immersed in water. Calculate the tension (force) in the cable before and after it is immersed in water.
All I am needing help on is the equations. Once I have the equation I can get the answers myself thank you!!

1 answer

gage pressure = density * g * height

absolute pressure = gage pressure + 1 atm (about 10^5 N/m^2 or Pascls)

Force = gage pressure * area
(use gage pressure because we assume one atm is pushing up from underneath)

tank volume = pi r^2 h

weight of gas = gas density * volume * g
(tis is the tension in the lifting cable with tank in air)

weight of water outside = buoyant force up = water density * (VOLUME) * g

Note about VOLUME of water displaced.
This tank will FLOAT because gasoline is less dense than water. There will be no tension in the cable unless the cable pulls the tank down.