Question

Chemical to reflect needle

Answer 1

mathematico-physical treatment of the floating (on water) needle system is presented. Gravitational potential energy, buoyancy, surface energy, and interfacial energy are taken into account. The floating is regarded as a metastable state resulting from a minimum in the curve relating the energy to the distance of descent. It is shown that such an energy minimum arises naturally out of the mathematics needed to evaluate the factors mentioned above. The calculations are supplemented with simple experiments with paper clips and an aluminum nail ("pseudo-needles"), which lead to approximate upper limits to the diameters of cylindrical metal rods of different densities that can be floated on water.