PRACTICE PROBLEMS IN HYDRAULICS – BUOYANCY
UNIVERSITY OF SAINT LOUIS TUGUEGARAO
CIVIL ENGINEERING DEPARTMENT
1) An iceberg (SG=0.917) floats in ocean water with 3000 m3 of the iceberg protruding above the
free surface. What is the volume of the iceberg below the free surface?
2) A can floats in the position shown.
What is its weight in Newtons?
3) It is desired to float in fresh water a wooden cone, 18 cm in diameter and 25 cm high, with the
apex downward. If the specific gravity of the cone is 0.60, determine the draft of the cone (Hint:
draft is the submerged height).
4) A sample of spherical rock hangs unto a string. The rock has a mass of 8 kilograms and it was
fully immersed into the oil that has a specific gravity of 0.83.
A) What is the radius of the rock when the tension in the string is 50 N?
B) If the rock was immersed into an unknown liquid and the string tension is 30 N, which of the
following is the value of the liquid’s density?
5) From the figure shown, the gate is 1.0 m wide
and is hinged at the bottom of the gate.
Compute the following:
A) The hydrostatic force acting on the gate
B) The location of the center of pressure
of the gate from the hinge
C) The minimum volume of concrete
(unit weight = 23.6 kN/m3) needed
to keep the gate in closed position
Prepared by: Engr. Jewell Arellano & Engr. Donn Panganiban
PRACTICE PROBLEMS IN HYDRAULICS – BUOYANCY
UNIVERSITY OF SAINT LOUIS TUGUEGARAO
CIVIL ENGINEERING DEPARTMENT
6) It is estimated that 90 percent of an iceberg’s volume is below the surface, while only 10 percent
is visible above the surface. For seawater with a density of 1025 kg/m 3, estimate the density of
the iceberg.
7) A cone floats in the glycerin (SG = 1.26), as shown in the figure. Find the mass of the cone.
8) It is said that Archimedes discovered his principle during a bath while thinking about how he
could determine if King Hiero’s crown was actually made of pure gold. While in the bathtub, he
conceived the idea that he could determine the average density of an irregularly shaped object
by weighing it in air and also in water. If the crown weighed 3.55 kgf (34.8 N) in air and 3.25 kgf
(31.9 N) in water, determine if the crown is made of pure gold. The density of gold is 19,300
kg/m3.
9) The density of a floating body can be determined by tying weights to the body until both the body
and the weights are completely submerged, and then weighing them separately in air. Consider
a wood log that weighs 1400 N in air. If it takes 34 kg of lead (𝜌 = 11,300 kg/m3) to completely
sink the log and the lead in water, Determine the average density of the log.
10) A wooden log with a circular cross section has a diameter of 4m and a length of 5m and is lying
down in a salted water (SG=1.2) partially submerged. The depth of submerged is 70% of the full
diameter of the log. Determine the specific gravity of the wood.
Prepared by: Engr. Jewell Arellano & Engr. Donn Panganiban
PRACTICE PROBLEMS IN HYDRAULICS – BUOYANCY
UNIVERSITY OF SAINT LOUIS TUGUEGARAO
CIVIL ENGINEERING DEPARTMENT
ANSWERS TO PROBLEMS:
1) 24345 m3
2) 4.99 N
3) 21.09 cm
4) A) 9.5 cm
B) 1413 kg/m3
5) A) 19.62 kN
B) 0.667 m
C) 0.3796 m3
6) 922.5 kg/m3
7) 1144.53R2
Prepared by: Engr. Jewell Arellano & Engr. Donn Panganiban
