Hydrostatic Force on the Plane Surface

1. FAKULTI KEJURUTERAAN MEKANIKAL
UiTM CAWANGAN TERENGGANU
KAMPUS BUKITBESI
e-LABORATORY ASSESSMENT REPORT
MEC294
THERMOFLUIDS LAB
EXPERIMENT :HYDROSTATIC FORCE ON PLANE SURFACE
DATE : 15/6/2020
PREPARED BY
GROUP :EM1104C(C4)
No Name Student ID
1 MUHAMMAD SYAHMI BIN MAWARDI 2018418218
2 MUHAMMAD SYAZWI BIN SHAMSHUZI 2018421394
3 NASIRAH HAZWANI BINTI NASIRUDDIN HAIKAL 2018699922
4 NURUL AMIRAH SYAFIQAH BINTI YA’ACOB 2018443228
5
SUBMISSION DATE :22/6/2020
LECTURER NAME :MADAM ASIAH BINTI AB. RAHIM
ASST. LECTURER NAME :
(For office use only)
ASSESSMENT
No. Item CO:PO Marks
Students Score (%)
S1 S2 S3 S4 S5
1.
Appearance,Organization,FrontPage,Formatetc (CO1:PO1)
5
Other (attendance, safety awareness etc) (CO1:PO1)
2. Objective and Theory (CO2:PO3) 5
3. Apparatus and Procedures (CO2:PO3) 5

2. 4. Result (data, graphs, sample calculation etc) (CO3:PO4) 10
5. Discussion (CO3:PO4) 15
6. Conclusion & Recommendation (CO1:PO1) 5
7. References (CO1:PO1) 5
TOTAL 50
COMMENTS

3. 1.0 Title
Hydrostatics Force on Plane Surface
2.0 Objective
❖ To determine experimentally the magnitude of the force of pressure (Hydrostatic force) and its
point of action (centre of pressure) on a plane surface.
❖ To compare the experimental results with the theoretical results.
3.0 Theory
Consider a plane surface submerged in a liquid as shown below
Diagram 3.1 shows the plane surface submerged in liquid with labels
Total pressure
It is the resultant force exerted by a static fluid on a surface when the fluid comes in contact with the
surface. It is also called hydrostatic force.

4. Centre of pressure
It is the point of the total pressure (hydrostatic force) on the surface.
Notes: For a rectangle surface
Diagram 3.2 shows the plane surface submerged in liquid with labels
Calculation of hydrostatic force and centre of pressure from experimental data

5. Case: Triangular profile of pressure distribution:
Case: Trapezoidal profile of pressure distribution

6. 4.0 Apparatus
(1) Rider (5) Water surface
(2) Stop pin (6) Water vessel
(3) Rotating slider (7) Appended weight
(4) Detent (α) Angle measurement
1
2
3
5
4
6
7
α

7. 5.0 Procedures
Part A: Vertical plane surface (α=0º)
1. By using detent (2), set the water vessel (1) to an angle of (α=0º).
2. Use rotating slider (3) to counterbalanced the unit. The stop pin (4) must be exactly in the middle
of the hole.
3. Mount the rider (6), and set any position with the lever arm. Chart the lever arm (the distance
between the rider and the water vessel rotation centre).
4. Place the appended weight (7) and record the value.
5. Add water to the water vessel (1) until it balances the unit (until the stop pin (4) is in the center
of the hole). Record water level (5) inside the vessel.
6. Repeat steps 4 and 5 for until 5 values of appended weight.
Part B : Inclined plane surface (α≠0º)
1. Repeat phases 1 and 2 of counterbalancing for a particular angle (α≠0º).
2. Repeat phases 3 to 6 of part A for measurement.

8. 6.0 Data and Calculation
Result from the Experiment;
Rectangular surface,h x b = 75 mm x 100 mm
Part A α=0°
Profile
Lever
arm
Appended
weight
Water Level Center of Pressure
Hydrostatic
Force(experiment)
Hydrostatic
Force(theory)
L(mm) Fԍ(N) S₁(mm)S₂(mm)S(mm) l(mm) h*(mm) F(N) F(N)
1 triangular 220 1 0 64 64 178.67 42.67 1.23 13.15
2 triangular 220 2 0 88 88 170.67 58.67 2.58 12.56
3 trapezoidal 220 3 0 104 104 134.57 38.57 4.90 9.90
4 trapezoidal 220 4 0 124 124 138.74 62.74 6.34 10.21
5 trapezoidal 220 5 0 144 144 141.13 85.13 7.79 10.38
Part B α=10°
Profile
Lever
arm
Appended
weight
Water Level Center of Pressure
Hydrostatic
Force(experiment)
Hydrostatic
Force(theory)
L(mm) Fԍ(N) S₁(mm)S₂(mm)S(mm) l(mm) h*(mm) F(N) F(N)
1 triangular 220 1 2 66 64 178.34 42.67 1.23 12.92
2 triangular 220 2 2 90 88 170.21 58.67 2.58 12.33
3 trapezoidal 220 3 2 106 104 135.01 40.00 4.89 9.78
4 trapezoidal 220 4 2 126 124 139.02 63.95 6.33 10.07
5 trapezoidal 220 5 2 146 144 141.34 86.23 7.78 10.24

9. Sample calculation:
Part A α=0°
Triangular
Ɩ = 200 -

cos
3
s
Ɩ = 200 -
0
cos
3
64
Ɩ = 200 - 21.33
Ɩ = 178.67 mm
h* =
3
2s
h* =
3
)
64
(
2
h* = 43.67 mm
Hydrostatic force(experiment)
F = G
F
L

F = )
1
(
67
.
178
220
F = 1.23 N
Hydrostatic force(theory)
F = ρցħA
F = (1000)(9.81)[0.178 sin (90 - 0)](7.5 x 10^-3)
F = 13.15 N

10. Trapezoidal
Ɩ = 150 -
)
50
cos
(
12
)
100
( 2
−

s
Ɩ = 150 -
)
50
0
cos
104
(
12
)
100
( 2
−
Ɩ = 150 -
)
50
104
(
12
10000
−
Ɩ = 150 - 15.43
Ɩ = 134.57 mm
h* = (Ɩ - 200) cos α + s
h* = (134.57 - 200) cos 0 + 104
h* = -65.43 + 104
h* = 38.57 mm
Hydrostatic force(experiment)
F = G
F
L

F = )
3
(
57
.
134
220
F = 4.90 N
Hydrostatic force(theory)
F = ρցħA
F = (1000)(9.81)[0.134 sin (90 - 0)](7.5 x 10^-3)
F = 9.90 N

11. Part B α=10°
Triangular
Ɩ = 200 -

cos
3
s
Ɩ = 200 -
10
cos
3
64
Ɩ = 200 - 21.66
Ɩ = 178.34 mm
h* =
3
2s
h* =
3
)
64
(
2
h* = 43.67 mm
Hydrostatic force(experiment)
F = G
F
L

F = )
1
(
34
.
178
220
F = 1.23 N
Hydrostatic force(theory)
F = ρցħA
F = (1000)(9.81)[0.178 sin (90 - 10)](7.5 x 10^-3)
F = 12.92 N

12. Trapezoidal
Ɩ = 150 -
)
50
cos
(
12
)
100
( 2
−

s
Ɩ = 150 -
)
50
10
cos
104
(
12
)
100
( 2
−
Ɩ = 150 -
)
50
60
.
105
(
12
10000
−
Ɩ = 150 - 14.99
Ɩ = 135.01 mm
h* = (Ɩ - 200) cos α + s
h* = (135.01 - 200) cos 10 + 104
h* = -64 + 104
h* = 40.00 mm
Hydrostatic force(experiment)
F = G
F
L

F = )
3
(
01
.
135
220
F = 4.89 N
Hydrostatic force(theory)
F = ρցħA
F = (1000)(9.81)[0.135 sin (90 - 10)](7.5 x 10^-3)
F = 9.78 N

13. 7.0 Discussion
From what we observe, this experiment have two method of calculation on how to get the value of
hydrostatic force which is by theoretical and also experimental method. The theoretical value of
hydrostatic force for both part have the higher value compared to the experimental one. This probably
happened due to some errors that occur when doing the experiment. One possible reason for the lower
experimental distances is that the weight is slightly larger than marked. There might be dirt, dust or debris
attached to the weight, causing the mass of the weight changed from the marked. Hence, this would
undervalue the experimental distance to the pressure centre. It is also possible that there have been
human error in reading the water height in the chamber. As a result, the error will cause false in
measurement and ruin the whole calculations. However, all the mistakes could be minimize by reading
the measurement carefully, clean all the sample before used and recheck the accuracy of the equipment
before used.
8.0 Conclusion
As a conclusion, we conclude that the experiment achieved all the main objectives stated above. It cannot
be denied that there are some errors occur during the experiment running consequently resulted the
differences between theoretical and experimental values. However, it can be solved by practising the
standard operation procedure of experiment and the precaution while running experiment. According to
the data the result that we get from experimental result are almost same with the theoretical result.
9.0 References
I. UiTM Fluid mechanics lecture notes
II. “Hydrostatics thrust on Submerged Plane Surface” – Retrieved from
https://nptel.ac.in/content/storage2/courses/112104118/lecture-5/5-
2_hydro_thrust_plane_surf.htm#:~:text=Equation%20(5.4)%20implies%20that%2
0the,5.2).– Accesed on 19th June 2020.
III. “Fluid Mechanics: Topic 4.1 - Hydrostatic force on a plane surface” – watched on
https://www.youtube.com/watch?v=0oHzBurIIpw – Accesed on 19th June 2020
IV. MEC 294 – Thermofluids Lab, Manual book