Weighing Things Under Water

Have you ever noticed that things weigh less under water? This activity explores this phenomenon.

Materials:

Label the rocks somehow, and weigh each one in air and under water. Here is a table you can use to enter your data (or you can use Excel to make the table, if you are going to use it to draw the graph in the next step).

A useful way to represent the results is to make an XY chart: each pair of values (weight in air, weight in water) becomes a point on the chart. You can draw this on the graph paper that is provided (or you can use Excel. Here are some instructions on how to use Excel this way).

Weigh the 2 newton weight in air and in water. Where would the corresponding point be on your chart? What does this tell us about this object?

Weigh a plastic bag containing some water (and no air) in air and in water. Where would its point be on your chart?
Check the box when you are done:   

Diver