Archimedes Principle - Example 8

Example 8:

Figure above shows a copper block rest on the bottom of a vessel filled with water. Given that the volume of the block is 1000cm³. Find the normal reaction acted on the block.
[Density of water = 1000 kg/m³; Density of copper = 3100 kg/m³]

Volume of the block, V = 1000cm³ = 0.001m³

Normal Reaction = R
Weight = W
Upthrust = F

Diagram below shows the 3 forces acted on the block.
All the 3 forces are in equilibrium, hence
R+F=W R=WF R= ρ 1 Vg ρ 2 Vg R=( ρ 1 ρ 2 )Vg =(31001000)(0.001)(10)=21N