To investigate the law of flotation
A measuring cylinder is about half filled with water and the reading noted. An ordinary test-tube with a cotton loop attached is then placed in the measuring cylinder, and lead shot added to the tube a little at a time until the tube floats upright (Fig. 12.6). The new water-level reading in the measuring cylinder is taken. The difference between this and the previous reading gives the volume of water displaced by the test-tube. Since the density of water is practically equal to I g/cm ‘, we can assume that the mass of water displaced is numerically equal to its volume in crrr’. The test-tube is removed from the cylinder, dried, and then weighed, using the cotton loop to attach it to the balance hook. The experiment is repeated several times, each time adding a little extra shot, and a table of results made out as shown. As usual we must be careful to express the mass of the test-tube and shot and also the mass of the water displaced in kilograms before multiplying by g (= 10 m/s2) in order to find their weights in newtons. If corresponding figures in the first and last columns of this table are found to agree, then the law of flotation is obeyed in this case.