1) The document reports on an experiment to determine the center of pressure on a vertically partially submerged plate. Various masses were used and the distance from the plate to the water surface was measured. 2) The center of pressure was calculated using a formula that takes into account the distance measurements, mass, and plate properties. The calculated and measured centers of pressure were compared to find percent error. 3) Results showed the center of pressure decreases with increasing mass and errors generally increased with lighter masses, with a maximum error of 40.49%. The relationship between calculated and measured centers of pressure was plotted on a graph.

1. University of Duhok
College of Engineering
Civil Department
Fluid Mechanics – Practical
Fluid Laboratory
A Report About :
Center of Pressure on Vertical Partially
Submerged Plate
Student Name : Jameel Masoud Jameel
Class : B
Date of Experimental : 14 / 12 / 2017
Date of Submitting : 11/ 1 / 2018
Experiment No. : 4

2. Procedure :
1) the distance from pivot to the balance pan must be noted if not
given. Check the straight of apparatus and Don’t vibrate the
apparatus during procedure.
2) Add water into the center of pressure's apparatus until
submerge partially plate of water.
3) Place weight to the balance pan and then fill out water by
opening drain cock until the beam level indicator stop in the
middle which is make a balance between water, weight in
balance pan and adjustable counterbalance.
4) Measure the distance from end face of torroid to the water
surface using the ruler (scale) that shown in the torroid.
5) Reaped the procedure. But just change the weight (decrease it)
and add water until the beam level indicator stop at middle and
measure the distance from end face of torroid to the water
surface again .

3. Calculations and Results :
We will calculate the Center of pressure by using this formula :
( hp )actual = y – d2 ( hp )theory = h́ +
IG
Ah́
Where : y =
ML
Ah́ , d2 = 20 – d1 , h́ =
𝑑1
2
Errors % =
( hp )theoryl− ( hp )actual
( hp )theory
× 100
Note :
A=𝟕. 𝟓 × 𝒅 𝟏 cm2
, L=27.5 cm , IG =
𝟕.𝟓×𝒅 𝟏
𝟑
𝟏𝟐
cm4
For example : Mass = 210 gm , d1 = 9.4 cm
A=7.5 × 𝑑1 = 7.5 × 9.4 = 70.5 cm2 , IG =
7.5×d1
3
12
=
7.5×9.43
12
= 519.115 cm4
h́ =
𝑑1
2
=
9.4
2
= 𝟒. 𝟕 𝐜𝐦
d2 = 20 − d1 = 20 − 9.4 = 𝟏𝟎. 𝟔 𝐜𝐦
y =
ML
Ah́
=
210 × 27.5
70.5 × 4.7
= 𝟏𝟕. 𝟒𝟑 𝐜𝐦
Center of pressure will be :
( hp )actual = y − d2 = 17.43 − 10.6 = 𝟔. 𝟖𝟑 𝐜𝐦
( hp )theory = h́ +
IG
Ah́
= 4.7 +
519.115
70.5 × 4.7
= 𝟔. 𝟏𝟕 𝐜𝐦
The error between the actual pressure's center and theory in (%) is :
Errors % =
( hp )theory− ( hp )actual
( hp )theory
× 100 =
6.17−6.83
6.17
× 100 = 9.61%

4. Detail's Table :
No.
Mass
(gm)
d1
(cm)
h́
(cm)
Y
(cm)
d2
(cm)
( hp )actual
(cm)
( hp )theory
(cm)
Errors
%
1 210.0 9.4 4.70 17.43 10.60 6.83 6.17 9.61 %
2 190.0 8.9 4.45 17.59 11.10 6.49 5.77 11.10 %
3 170.0 8.4 4.20 17.67 11.60 6.07 5.38 11.41 %
4 150.0 7.8 3.90 18.08 12.20 5.88 4.91 16.43 %
5 100.0 6.2 3.10 19.08 13.80 5.28 3.74 29.12 %
6 50.0 4.3 2.15 19.83 15.70 4.13 2.46 40.49 %
The relationship between the actual pressure's center sand theory is :
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7
(hp)theory
( hp )actual
Relationship between (hp)actual and ( hp )theory

5. Discussion and Conclusion :
In this test we determine the Center of pressure on vertical Partially
submerged plate, and finally we got a result after doing all procedure
accuracy, which is different pressure's center with different weight. as
shown in result, with increasing weight the distance form center of
pressure to surface of water will decrease, and the force in the center of
pressure will be decrease. in this test we calculate the center of pressure
by two methods which is actual and theory, the difference between it, is
the errors in actual measurement. we have some errors but it doesn’t
mean that our test is wrong, because every test have some errors, in our
test the maximum error is (40.5 %) which greater than (10 %), therefore
from determining errors we can say our test is correct. we know that if
we do many tests we will get the right average and the result will be very
accuracy.
In conclusion the purpose of this test is to determine the actual center of
pressure, compare it with theory of pressure's center, the errors that we
have in actual pressure's center and how we can calculate the center of
pressure in actual. finally we will get and determine the center of
pressure and errors, to know our test was correct or not.