A metal piece of mass 160 g lies in equilibrium inside a glass of water (figure 13-E4). The piece touches the bottom of the glass at a small number of points. If the density of the metal is 8000 kg m4, find the normal force exerted by the bottom of the glass on the metal piece.


The Metal pieces completely immersed in water.

Given, density of metal,


Mass of metal,


Therefore, Volume of metal immersed,


Therefore, weight of the water displaced (or the buoyant force),


Now we balance the vertical forces. These vertical forces consist of the normal reaction(N) from the surface (upwards), the weight of the metal(downwards) and the buoyant force(upwards).




Hence the normal reaction (which is due to the metal touching the surface at different points) is 1/4 N in total.


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