TRIBHUVAN UNIVERSITY
INSTITUTE OF ENGINEERING
THAPATHALI CAMPUS
Lab report on Hydrostatic Forces on Submerged Bodies
Submitted by: Submitted to:
Name: Bishal Kamali Mechanical Department
Roll no.: THA077BME016
Date: 2079/12/03
TITLE: "HYDROSTATIC FORCES ON SUBMERGED BODIES"
OBJECTIVES:
• To determine the hydrostatic forces of fully submerged bodies in terms of
moment by center of pressure method and compare this with the theoretical
value.
APPARATUS REQUIRED:
i. Quadrant curved surface attached to adjustable counter balance (Hydrostatic
Pressure Apparatus)
ii. Weights
iii. Scale
iv. Graduated Water Box or Tanks
THEORY:
CG is the point in the body surface where total weight of the body is assumed to be
concentrated. Centre of Pressure is the point where the total sum of pressure force
(resultant force) acts on a body causing force to act through that point.
When the quadrant is immersed by water addition to the tank, hydrostatic forces applied
to the vertical surface of quadrant can be determined by considering as, the hydrostatic
force at any point on the curved surface is normal to the surface and resolves through
pivot point. Hydrostatic forces on upper and lower surfaces, therefore, have no net
effect, no torque present to affect equilibrium.
The forces on side of quadrant are horizontal and cancel each other. The hydrostatic
force on vertical submerged face is counteracted by the balance weight. The resultant
hydrostatic force can, therefore, be calculated from value of balance weight and depth
of water.
The system is in equilibrium if the moments generated about pivot point by hydrostatic
force and added weight are equal.
The moment about the pivot of water pressure on immersed plane vertical face is
measured followed by the moment experimentally measured by the mass at certain
distance from knife edge.
Here,
𝐼
Position of center of pressure (CP), h = + 𝑦
𝐴 𝑦
Where, y = depth of centroid = y-d/2
y = bottom edge of plane below water surface
𝑑 𝑑2
Distance of CP from pivot = 𝑎 + 2 + 12𝑦
Where, a= distance of top edge of plane surface from pivot axis
b = width of plane surface (breadth of quadrant)
d = depth of plane surface (height of quadrant)
𝑏𝑑3
I = moment of Inertia = 12
Force (Hydrostatic force), Fth = *A*y
Theoretical Moment, Mth = F * (y*+a – (y – d))
Actual Moment (experimental), Mexp = mg*L
PROCEDURE:
1. Apparatus was placed on a level table.
2. a, b and d were measured in meter.
3. With no water in apparatus, it was checked that plane face was vertical and
a preliminary balance was made by using the empty mass longer and the
adjustable screw at the end. In the balanced position, the beam just lifted off
its desirable preset stop.
4. Water was added to the quadrant until the level of water was just above the
top edge of the plane under test.
5. At that stage, masses were added in the mass area until the balance was
restored. y1 and W1 were noted.
6. The procedure were repeated for 3 more readings.
OBSERVATION:
Moment Arm (L) = 27.9 cm = 0.273 m
Breadth of Plane Surface (b) = 7.5cm = 0.075 m
Depth of plane surface (d) = 10.1 cm = 0.1 m
Distance up to edge of plane surface from pivot axis plane (a) = 0.099 m
Area (A) = 0.007474m2
Force
Mass (N) Mexperimental Depth Mtheoretic
S.N. Added F= = of water y = (y- y* force al (Nm) % error
(kg) m*9.81 F*L(Nm) (y) m d/2) m
0.250 2.4525 0.6695 0.109 0.0585 0.07302 4.29 0.69935 4.26%
1
0.270 2.6487 0.723 0.113 0.0625 0.07609 4.58 0.7424 2.61%
2
0.290 2.8449 0.776 0.119 0.0685 0.08090 5.02 0.8077 3.92%
3
0.310 3.0411 0.83 0.123 0.0725 0.08421 5.31 0.851 2.46%
4
0.340 3.3354 0.91 0.130 0.0795 0.09018 5.82 0.926 1.72%
5
0.360 3.5316 0.964 0.134 0.0835 0.09367 6.12 0.9710 0.72%
6
RESULT
Forces on the submerged body are F1 =4.29N, F2 = 4.58N, F3 = 5.02N, F4 = 5.31N, F5
=5.82N, F6=6.12N
CONCLUSION:
The hydrostatic force lab report is an experiment that describes the behavior of fluids
when subjected to forces. This experiment involves studying the forces exerted by a
liquid on a surface when submerged under the liquid. Through this experiment, we were
able to study Archimedes' principle, which states that the buoyant force acting on an
object is equal to the weight of the fluid displaced by the object. From the data collected
during the experiment, we were able to conclude that the hydrostatic force increases
with depth, as the pressure of the liquid increases with depth. We also determined that
the hydrostatic force is dependent on the density of the liquid and the area of the object
submerged in the liquid. It was also determined that the force acted on the object is in
the upward direction, which is why the object tends to float in the liquid.
PRECAUTIONS:
1. Masses should be added carefully until balance is restored.
2. Data should be taken carefully.
TRIBHUVAN UNIVERSITY
INSTITUTE OF ENGINEERING
THAPATHALI CAMPUS
Lab report on Verification Momentum Equation
Submitted by: Submitted to:
Name: Bishal Kamali Mechanical Department
Roll no.: THA077BME016
Date: 2079/12/03
