Pressure variance with depth of fluid: Quantitative Observational Experiment

Aim

Find a pattern relating the pressure in a fluid to depth in the fluid.

Prior Knowledge

  1. Graphing skills
  2. Knowledge of the relationship between pressure and volume of a gas.

Description of the Experiment

A tube, sealed at one end, is placed vertically with its open end submerged in a beaker of water, thus enclosing a volume of air in the tube. As the tube is lowered in the water, you can see that the water starts occupying the lower part of the tube.

Your objective is to discover a rule relating the pressure in the fluid at some level to the distance of that level from the surface of the fluid.

Addtional Information

An observant person will note that the requirements of this experiment and the pressure vs volume experiment are circular. If you can come up with a better experiment which will allow an experimenter to construct a quantitative rule between pressure and depth in a fluid, please email us. We cannot pay royalties, but we will acknowlege you.

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Questions

  1. Description: what did you observe in the experiment?
    • How is the change in height of the water in the tube related to the change in volume of the gas?


    • How is the depth of the mouth of the tube in the water related to the pressure inside the liquid?


    • How is the depth of the mouth of the tube in the water related to the pressure of the gas inside the tube?
  2. Explanation

    How can you use the changes in volume of the gas in the tube to tell what the pressure in the fluid is at that point?. Using the data that you have collected, construct a rule relating the pressure in the fluid at the mouth of the tube to the depth of the mouth in the fluid.

  3. Maths skills

    Refer to the discussion about graphing in the observational experiment: discovering the relationship between pressure and volume of a gas.