Introduction and Objectives
Pressure is one of the most important
physical quantities; it is involved in almost all fields, ranging from fluid
and solid mechanics to thermodynamics (Arnal & Millan, 2013). It’s safe to
say that pressure is a scalar physical quantity that has its own magnitude but
no direction. It is actually the force applied perpendicularly to every unit
area of the given surface. It is possible to express pressure in the form of
units, depending on the context of use (Delplace, 2016). A solid exerts a
particular pressure on the surface upon which it remains in contact. Similarly,
gases and liquids exert particular pressures on their relevant objects or
surfaces.
The core objectives of this lab are as
follows:
1. To
determine the specific weight of a fluid sample.
2. To
visualize and understand the pressure are different points of a system,
concluding that the pressure varies with depth.
3. To
conclude that the pressure remains constant on a horizontal plane.
4. To
verify that at a given depth, the pressure remains same both on an angled
surface and a vertical surface.
5. To
conclude that the pressure can increase linearly if the weight in a cylinder or
piston increases.
Equipment/Apparatus and Method
a. A
graduated cylinder was required for this lab experiment in order to measure the
volume of the given liquid as well as to determine its weight.
b. Another
thing that we used to measure the weight was the PASCO Force Sensor, which was
mounted on the balance setup.
c. The
PASCO Pressure Sensor and the PASCO Temperature Probe were used to measure the
temperature and pressure of the given liquid.
d. All
of these sensors were carefully connected to the PASCO PowerLink device.
Part A: Method or Procedure -- Verifying the
Specific Weight
1. We
used a graduated cylinder, the temperature probe, the PASCO weight scale with
the force transducer, salt water and cooking oil to determine the weight of
every solution.
2. The
PowerLink device was connected to the computer system, and then we installed
the temperature probe and the force balance in the PowerLink. At this point, we
ensured that the force balance before starting the experiment was zero.
3. Then
we started the data collection software and measured the weight of the empty
container, followed by recording the value.
4. A
specific amount of the liquid was added to the container, and then we recorded
the value as well as measured the volume.
5. The
temperature of the liquid was measured with the help of the temperature probe,
and then we recorded the results.
6. In
the next step, we placed the container on the scale and recorded the weight.
7. The
same process was repeated four to seven times using different volumes.
8. The
weight of empty container was subtracted from the total number of measured
weight in order to find out the actual weight of the given liquid. Then we
recorded the weight on the data form and calculated γ (gamma-specific weight)
by dividing the weight by the volume. The average of every lab experiment was then
taken.
9. For
the container that had water in it, we used the water temperature data to
verify the specific weight of the solution.
10. This
step was repeated four to six times using the cooking oil and the salt water
solution. In addition to the specific weight, we determined specific gravity
(S) of all the liquids by dividing the specific weight of each of them by the
specific weight of water.
11. The
hydrometers were used for measuring the specific gravity of given solutions.
Part B: Method or Procedure – Measuring the
Pressure at Various Points in a System
1. First
of all, we designed a data collection form for recording the information.
2. The
water column apparatus was filled with sufficient water, and its level was kept
below the top of the column.
3. Then
we used a tape measure for recording the depth of every pressure tap. We
referenced our measurements from a certain, fixed point on the device.
4. The
PASCO temperature probe was then used for measuring the temperature of the
given liquid and for recording the data accurately.
5. In
the next step, we used the PASCO pressure transducer for measuring the
atmospheric pressure and made sure that there was no water in the tube
connecter to the sensor as this could cause the current to flow from the tube
and could hinder our experiment. The result was recorded at this stage.
6. In
the next step, we made use of the PASCO pressure transducer for getting the
pressure at every location, and for recording the results. This value was the
absolute pressure.
7. The
experiment was repeated two to three times in order to determine the accurate
pressure datasets.
8. With
the help of a screwdriver, we opened the ports on the side of the device and
observed the water as it discharged.
Part C – Procedure or Method – Verifying the
Relationship of Weight and Pressure
1. This
was done with the help of the pressure-gauge calibration unit.
2. We
measured and recorded the diameter of the piston in the first step, which was
attached to the weight carrier.
3. Then
we recorded the listed theoretical pressure for every weight, followed by
closing the valve on the side of the oil pump. This was done to prevent the
pumped oil from leaking or draining.
4. The
protective cap was removed till the time the pump oil was evenly distributed,
starting from the top.
5. The
pressure was then recorded with the oil exposed to the atmospheric pressure.
6. In
the next step, we took the cylinder and placed the weight carrier on it by
inserting the piston and lowering the oil by opening the valve until or unless
the contact was made.
7. Then
we closed the valve and slowed down the speed of pump oil till the weight
carrier lifted off the cylinder. It was found to be floating on the oil, and
this is when we recorded the pressure.
8. The
weight was the position with the help of a pressure of 0.166 bar onto the
weight carrier, and we ensured that it sat flat and was anchored by the
alignment pin. At this stage, we verified the assembly was still floating on
the oil, and then we recorded the pressure.
9. In
the next step, we added one (1) of the four (4) 0.500 bar weights to the weight
carrier. Then we verified the assembly was floating on the surface and recorded
the pressure.
10. The
fourth step was repeated for each of the remaining three weights.
Discussion
Part
A
From this data, it is evident that the weight
of the empty cylinder was something around 583 grams, and the weight of the
empty salt water cylinder was approximately 204 grams. When the data is
compared with the information provided to us, we got to know that the weight of
a cylinder or body is directly proportional to the force or pressure being
exerted on it. A graduated cylinder was used along with the PASCO weight scale
and the temperature probe for determining the weight of all solutions. When the
cylinder was empty, its weight was not as much as it was when the solution was
added to it. By combining the weight of both the solution and the cylinder, we
were able to subtract the weight of cylinder from the total weight in order to
find out the actual weight of the solution. The collection of data started when
the PowerLink device was connected to the computer system, and this allowed us
to properly install the temperature probe and the force balance in the
PowerLink. As we began adding some liquid to the container, we were able to
record the value and to measure the volume, which was 8.75 grams for the
solution of salt water and 718 grams for another solution. The container was
also placed on the scale in order to record the actual weight, which was
something around 250, 375 and 500 with oil in the solution/container/cylinder.
This process was repeated several times with varying volumes in order to obtain
the accurate or desired results. The calculation of γ (gamma-specific weight)
was done by dividing the weight by the volume, and the average of every lab
experiment was then taken, which was 291, 402, 516 and 632 respectively. By
repeating the same process for four to six times using the cooking oil and the
salt water solution, we were able to determine the gravity of the given
liquids. For this purpose, we had to divide the specific weight of every
solution by the specific weight of water.
Part
B
In the second part of this lab experiment,
the values we obtained where 33.75, 21.75, 15.75, 9.75 and 3.75 respectively.
The sixth time we repeated the experiment, the value obtained was 8.5 in. In
order to obtain these values, we had to fill the water column apparatus and
used a tape measure. The PASCO temperature probe was used for measuring all of
these quantities. The temperature, as well as the atmospheric pressure, was
recorded using the same instrument/equipment. The temperature was recorded as
18.5 degree Celsius, 18.6, 18.7, 18.5 and 19.1 degree Celsius. The PASCO
pressure transducer was then used to record the pressure at every stage, and we
repeated this experiment several times with an aim to find out the accurate
pressure datasets. A screwdriver helps us open the ports on the side of the
device, and then we observed the water as it discharged. One thing we noticed
during this part of the experiment was that the equipment kept leaking, and
this made it difficult for us to continue the experiment, but we still managed
to record or determine these values.
Part
C
In Part C of this lab experiment, we used a
pressure-gauge calibration unit, measured and recorded the diameter of the
piston, which remained attached to the weight carrier for some time. The piston
rings were marked 1, 2, 3, 4 and 5, and the weight on all of them was 192.7,
583.8, 581.3, 581.3 and 581.8 respectively. In order to allow the pump oil for
distributing evenly, we had to remove the protective cap for some time. At this
stage, the pressure was recorded to be 0.3, 0.5, 1.05, 1.55, 2.05 and 2.55
respectively. We positioned the weight with the help of the pressure bar of
0.166 which was placed onto the weight carrier. Here we made sure that the
pressure bar was sitting flat on the weight carrier and anchored by the
alignment pin. We were then able to verify the assembly and recorded the
pressure. This was the same time when we had to add one (1) of the four (4)
0.500 bar weights to the weight carrier. In the next step, we verified the
assembly on the surface and repeated the experiment several times for all of
the given weights. The temperature during this part of the experiment was tried
to be kept 10.8 degree Celsius. Here the pressure(P) is the total pressure,
which means from the data P Ring#1. 0.55 Bar= total P for the piston and
ring#1. P ring #2 = P piston+P ring #1+P ring #2.
Conclusion
In the fields of engineering and physics, fluid
dynamics is considered an integral sub-discipline since it helps describe how
the fluid flows (Arnal & Millan, 2013). Some of its sub-disciplines are
aerodynamics and hydrodynamics. In our lab experiment, we had paid much
attention to the accuracy of data as well as to the atmosphere, and we tried to
keep the temperature at every stage maintained so that correct results could be
obtained. Fluid dynamics is a systemic structure that helps us embrace
semi-empirical and empirical laws at the same time, which are derived from the
flow measurement and are used to solve various practical problems.
References
Exercises in Fluid Mechanics.
(n.d.). Fluid Mechanics, 69-138. doi:10.1007/3-540-27223-2_3
Arnal, D., & Millan, P.
(2013). Measurement Needs in Fluid Mechanics. Laser Velocimetry in
Fluid Mechanics, 1-13. doi:10.1002/9781118569610.ch1
Delplace, F. (2016). Fluid
Mechanics at Atomic Scale. Fluid Mechanics: Open Access, 03(02).
doi:10.4172/2476-2296.1000133
