This simulation illustrates the concept of the buoyant force. The goal is to determine the density of two uknown blocks by measuring their apparent weight or percentage submerged in water, which has a known density of 1000kg/m^3. Then, once the block densities are known, use that information to determine the density of an unknown fluid.
The buoyant force is the upward force exerted on an object by a fluid when the object is partly or entirely immersed in the fluid.
In this simulation we place a block with a known weight in air, but an unknown density, into a container of fluid. The block is suspended from a force meter (not shown in the simulation) displaying its apparent weight while in the fluid, and the percentage of the volume of the object that is submerged in the fluid is also displayed. When the object is floating (less than 100% submerged) it has no apparent weight because it is in equilibrium. When the object is fully submerged its apparent weight is its weight in air, due to the force of gravity, minus the buoyant force pushing it back up while it's in the fluid. An object's weight equals its mass multiplied by the acceleration due to gravity, g, and is in units of Newtons when the units of mass are kilograms.
The buoyant force is given by Archimedes' principle, which states that the buoyant force is equal to the weight of the fluid displaced, which is equal to the density of the fluid multiplied by g multiplied by the volume of fluid displaced by the object.
Recall that mass equals density times volume, which means that volume equals mass divided by density. Thus it is not necessary to know the exact volume of the object being submerged, only its mass in air and the percentage of its volume that is submerged in the fluid or its apparent mass if it's fully submerged in the fluid.
Modified from a simulation originally written by Andrew Duffy, and first posted on 11-17-2018.