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Fluids Experiment: Show Weight in Water is Less than in Air

by Ron Kurtus (updated 21 November 2022)

You may have noticed that objects seem to weigh less when under water than when they are held outside the water. Perhaps you have noticed this when you were swimming and picked up something off the floor of the pool or lake.

This can be an idea for a science project in the area of Physical Science. You can measure the weight of an object in air and in water to demonstrate the physical law.

Questions you may have include:

This lesson will answer those questions.

Purpose of experiment

The purpose of this experiment is to demonstrate that an object that does not float actually weighs less in water than in air.


Not much research is required for this experiment, since it is a demonstration. You could do some preliminary examinations to see which liquids do not mix into solutions.


Select materials and then follow the procedure.



  1. Weigh object in air and record weight
  2. Place under water and weigh again
  3. Comparer measurements

Keep records

If this is going to be an experiment for a science fair, you will need to record your activities in a log book.

Draw conclusions

You can draw conclusions about the relationship between weight in air and in water.

Write report

Write up a report to summarize your results and your proposed solution to the problem.


You have proven that objects weigh less in water than in air. Why is that so?

Consider the possibilities

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Fluids Experiment: Show Relationship Between Weight in Air and in Water

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