Because the molecules are moving so fast, gases have strong intermolecular forces acting. The density of a 5 kg chunk of iron is smaller than the density of a 10 kg chunk of iron. If two objects have the same density they must have the same weight. The density of copper is a unique property of copper. If two objects have the same density they must have the same volume.
Density is only useful when describing solids.
Suppose that in a particular hydraulic system, the larger piston has ten times the diameter of the smaller piston. Consider four flasks of different shapes, as shown. 2 c. Flask 3 d. Flask 4. 5.We know that a rock sinks in water. There is no buoyant force on the rock because it is sinking.