Archimedes’ Principle - General Physics Lab, Study notes of Physics

Download Archimedes’ Principle - General Physics Lab and more Study notes Physics in PDF only on Docsity! General Physics Lab Handbook by D.D.Venable, A.P.Batra, T.Hübsch, D.Walton & M.Kamal Archimedes’ Principle 1. Theory We are aware that some objects float on some fluids, submerged to differing extents: ice cubes float in water almost completely submerged, while corks float almost completely on the surface. Even the objects that sink appear to weigh less when they are submerged in the fluid than when they are not. These effects are due to the existence of an upward ‘buoyant force’ that will act on the submerged object. This force is caused by the pressure in the fluid being increased with depth below the surface, so that the pressure near the bottom of the object is greater than the pressure near the top. The difference of these pressures results in the effective ‘buoyant force’, which is described by the Archimedes’ principle. According to this principle, the buoyant force FB on an object completely or partially submerged in a fluid is equal to the weight of the fluid that the (submerged part of the) object displaces: FB = mf g = ρfV g . (1) where ρf is the density of the fluid, mf and V are respectively mass and the volume of the displaced fluid (which is equal to the volume of the submerged part of the object) and g is the gravitational acceleration constant. 2. Experiment Object: Use Archimedes’ principle to measure the densities of a given solid and a provided liquid. Apparatus: Solid (metal) and liquid (oil) samples, beaker, thread, balance, weights, stand, micrometer, calipers, PASCO Science Workshop Interface, Force Sensors and a Macintosh Computer. Part a.: A solid object of volume V , heavier than water. When completely submerged in water, the buoyant force is FB = ρwV g , (2) where ρw is the density of water. The mass of the object, Ma, when weighed in air is given by Ma = ρsV , (3) where ρs is the density of the solid. The apparent weight of the object, Mwg, when immersed in water is the difference between its weight in air and the buoyant force: Mwg = Mag − ρwV g . (4) Therefore, Mw = Ma − ρwV = Ma − ρw Ma ρs , (5) ρs = Maρw (Ma −Mw) . (6) Archimedes’ Principle: page 1