ECH 141
Problem Set #2
1.
A rectangular tank 7 m wide is layered with 8 m of oil (
ρ
= 880 kg/m
3
), 6 m of water, and
4 m of mercury (
ρ
= 13,600 kg/m
3
). The tank is surrounded by air at atmospheric pressure and the
top is open.
Calculate the total force on the side of the tank.

2.
Some claim that Archimedes discovered the buoyancy laws when asked by King Hiero of
Syracuse to determine whether or not his crown was pure gold (specific gravity = 19.3).
Archimedes found the weight of the crown in air to be 13.0 N and in water to be 11.8 N.
Was the crown made of gold?
Explain your reasoning.