A 15N block is immersed in a salt water (density = 1030 kg/m3). Determine the buoyant force acting on the block if the spring scale reads 11.8 N.

The weight of the block is 15 N. If the scale says 11.8 N, there must be a buoyancy force of 3.2 N, not matter what the fluid densty or fractional immersion is.