A simple method based on the moment of forces and Archimedes' principle is described for finding density without measuring the mass and volume of an object. The method involves balancing two unknown objects of masses M1 and M2 on each side of a pivot on a metre rule and measuring their corresponding moment arms. The object whose density is to be found is then immersed in a liquid of known density and the new moment of the arm of this object is measured. The density of the immersed object is then determined using only its measured moment arms and the density of the liquid.
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