Question

A common brick is about 1.8 times denser than water. what is the apparent weight of a 0.20 m3 block of bricks under water?

Answer 1

Pressure of .2 m^3 of bricks:

Pb = ρ g H = 1.8 ρw * 9.80 m/s^2 * .20 m = 1800 * 9.8 * .2 = 3530 Pascals

ρb = 1.8 ρw = 1.8 since the density of bricks is 1.8 that of water

Pw = 1 * 9.8 * 1000 * .2 = 1960 Pascals

W = P * A pressure * Area = Force

Pnet = 1570 Pascals - pressure due to bricks under water

F = 1570 N/m^2 * .2m^2 = 63 N force on pile of bricks