To investigate Archimedes’ principle for a body in liquid
A displacement can is placed on the bench with a beaker under its spout (Fig. 12.2). Water is poured in until it runs from the spout. When the water has ceased dripping the beaker is removed and replaced by another beaker which has been previously dried and weighed. Any suitable solid body, e.g., a piece of metal or stone, is suspended by thin thread from the hook of a spring-balance calibrated in newtons and the weight of the body in air is measured. The body, still attached to the balance, is then carefully lowered into the displacement can. When it is completely immersed its new weight is noted. The displaced water is caught in the weighed beaker. When no more water drips from the spout the beaker and water are weighed. Owing to the difficulty in weighing a beaker containing water with an extension spring balance, we shall probably use an ordinary balance which gives mass readings
and hence find the weights of the beaker and displaced water by multiplying the masses by g, assumed equal to 10 mjs2 (page 40).
The results should be set down as follows:
Weight of body in air = N
Weight of body in water = N
Weight of empty beaker = N
Weight of beaker plus displaced = N
Apparent loss in weight of body = N
Weight of water displaced = N
If the apparent loss in weight of the body, or the upthrust on it, is found equal to the weight of the water displaced, then Archimedes’ principle is verified in the case of water. Similar results are obtained if any other liquid is used.