Technological Institute of the Philippines 983 Aurora Boulevard, Cubao, Quezon City
College of Engineering Civil Engineering Department
CE405 – Fluid Mechanics Experiment # 5
Specific Gravity by Archimedes Principle
Submitted by:
Malvecino, Juztine M. (Leader) Espino, Pamela Shara L.
Franco, Rebi Jennise J. Macatangay, Jesuzette L.
Torcatos, Mark Lester C. Victorio, Ace Louise B.
Group 3 – CE41FB6
Submitted to: Engr. Steve Sarsonas
Date of Submission: August 24, 2015
CE405/CE41FB6
Malvecino, Juztine M.
Observation:
The hydrometer gives approximate specific gravity results when submerged into the liquid. Conclusion:
I conclude that the buoyant force does not increase even if the depth is increasing. Only its pressure is increasing.
Espino, Pamela Shara L.
Observation:
I observed that the greater the density, the tighter or closer the molecules are packed inside the substance. Therefore, the greater the density / specific gravity of a liquid the higher a hydrometer will be buoyed by it.
Conclusion:
Therefore I conclude that any object totally or partially immersed in any fluid is lifted up by a force equal to the weight of the fluid that is displaced.
Franco, Rebi Jennise J.
Observation:
Based on the experiment I observe that the hydrometer shows a not so accurate specific gravity when it was release into the liquid.
Conclusion:
I therefore conclude that when the hydrometer was submerge it will affect the measurement of specific gravity because the more that the depth is increasing, the buoyant force stays the same.
Macatangay, Jesuzette L.
Observation:
In our previous experiment, simply using graduated cylinder and hydrometer, we got the specific gravity of our sample liquids. Specific gravity is the ratio of the density of a substance to the density (mass of the same unit volume) of a reference substance.
Conclusion:
Specific gravity varies with temperature and pressure; reference and sample must be compared at the same temperature and pressure or be corrected to a standard reference temperature and pressure. Substances with a specific gravity of 1 are neutrally buoyant in water. Those with SG greater than 1 are denser than water and will, disregarding surface tension effects, sink in it. Those with an SG less than 1 are less dense than water and will float on it. In scientific work, the relationship of mass to volume is usually expressed directly in terms of the density (mass per unit volume) of the substance under study.
Torcatos, Mark Lester C.
Observation:
I observed that the hydrometer helps us find the specific gravity of a certain liquid easily. It shows the result instantly after you release the hydrometer from your hand.
Conclusion:
I therefore conclude that soy sauce has the highest specific gravity and oil has the lowest in the four liquids. When the depth is increasing, the pressure is also increasing. The data that the hydrometer shows will not be that accurate because of small errors in recording it.
Victorio, Ace Louise B.
Observation:
I observed that the hydrometer interacts to the buoyant force acting on it to determine the liquid's specific gravity.
I conclude that the specific gravity of a fluid greatly affects how deep an object can float.
Experiment 5
Specific Gravity by Archimedes Principle Objective:
The activity aims to determine the specific gravity of fluid using Archimedes Principle. Intended Learning Outcomes (ILOs):
At the end of the activity, the students shall be able to: 1. Discuss the concept of Archimedes principle. 2. Demonstrate the proper use of hydrometer.
3. Identify the correct measurement of the specific gravity of a fluid using hydrometer.
Discussion:
Buoyancy is an upward force exerted by a fluid that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the column than at the top. This difference in pressure results in a net force that tends to accelerate an object upwards. The magnitude of that force is proportional to the difference in the pressure between the top and the bottom of the column, and (as explained by Archimedes' principle) is also equivalent to the weight of the fluid that would otherwise occupy the column, i.e. the displaced fluid.
For this reason, an object whose density is greater than that of the fluid in which it is submerged tends to sink. If the object is either less dense than the liquid or is shaped appropriately (as in a boat), the force can keep the object afloat. This can occur only in a reference frame which either has a gravitational field or is accelerating due to a force other than gravity defining a "downward" direction (that is, a non-inertial reference frame). In a situation of fluid statics, the net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body.
Operation of the hydrometer is based on “Archimedes Principle” that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced by the submerged part of the suspended solid. Thus, the lower the density of the substance, the farther the hydrometer will sink.
Fb=γfVs
Where,
Fb = Buoyant Force
Vs = Volume submerged Resources / Instruments Required:
Graduated Cylinder
Hydrometer
Liquids
Procedures:
1. Pour an amount of liquid into the graduated cylinder. 2. Place the graduated cylinder on a level surface.
3. Gently lower the hydrometer into the graduated cylinder. If there are bubbles clinging to the hydrometer, flick it to knock them off. If this does not get rid of the bubbles, remove the hydrometer and lower it again. Bubbles throw off the hydrometer reading.
4. Move the hydrometer to the middle of the graduated cylinder so it is floating freely and not attached to the sides.
5. Take the measurement at the lowest point of the curved surface of the liquid.
Laboratory Report:
Group No: 3 Section: CE41FB6
Date Performed: August 17, 2015 Date Submitted: August 24, 2015
Group Members: Malvecino, Juztine M. (Leader) Espino, Pamela Shara L.
Franco, Rebi Jennise J. Macatangay, Jesuzette L. Torcatos, Mark Lester C. Victorio, Ace Louise B.
1. Data and Results:
LIQUID SPECIFIC GRAVITY
Water 1.0
Oil 0.91
Vinegar 1.1
2. Observation:
We observed that the hydrometer interacts to the buoyant force acting on it to determine the liquid's specific gravity. The hydrometer helps us find the specific gravity of a certain liquid easily. It shows the result instantly after you release the hydrometer from your hand. The greater the density, the tighter or closer the molecules are packed inside the substance. In short, the hydrometer gives approximate specific gravity results when submerged into the liquid.
3. Analysis:
4. Source/s of Error/s:
The sources of error would be the estimated gathering of data on the hydrometer since we can’t get the exact value of reading with just using our naked eye.
5. Conclusion:
We therefore conclude that the specific gravity of a fluid greatly affects how deep an object can float. The soy sauce has the highest specific gravity and oil has the lowest in the four liquids. When the depth is increasing, the pressure is also increasing. Any object that is totally or partially immersed in any fluid is lifted up by a force equal to the weight of the fluid that is displaced. The buoyant force does not increase even if the depth is increasing. Specific gravity varies with temperature and pressure; reference
and sample must be compared at the same temperature and pressure or be corrected to a standard reference temperature and pressure.
Assessment (Rubric for Laboratory Performance):
CRITERIA
BEGINNER
1
ACCEPTABLE
2
PROFICIENT
3
Score
I. Laboratory Skills Manipulative Skills Members do not demonstrate needed skills Members occasionally demonstrate needed skills Members always demonstrate needed skills Experimental Set- upMembers are unable to set-up the
materials
Members are able to set- up the materials
with supervision
Members are able to set – up the material
with minimum supervision Process Skills Members do not demonstrate targeted process skills Members occasionally demonstrate targeted process skills Members always demonstrate targeted process skills Safety Precautions Members do not follow safety precautions
Members follow safety precautions most of the
time
Members follow safety precautions at all times II. Work Habits
Time Management / Conduct of experiment
Members do not finish on time with
incomplete data
Members finish on time with incomplete data
Members finish ahead of time with complete data and time to revise
data
Cooperative and Teamwork
Members do not know their tasks and
have no defined responsibilities. Group conflicts have
to be settled by the teacher
Members have defined responsibilities most of the time. Group conflicts
are cooperatively managed most of the
time
Members on tasks and have defined responsibilities at all times. Group conflicts
are cooperatively managed at all times
Neatness and Orderliness
Messy workplace during and after the
experiment
Clean and orderly workplace with occasional mess during
and after the experiment
Clean and orderly workplace at all times
during and after the experiment Ability to do independent work Members require supervision by the teacher Members require occasional supervision by the teacher
Members do not need to be supervised by
the teacher
RATING = ( 24 TotalScore ) x 100% Water Oil
Vinegar Soy Sauce Questions and Problems:
1. A rectangular solid piece of wood 30 cm2 and 5 cm thick floats in water to a depth of 3.25 cm. How heavy an object must be placed on the wood (s=0.50) in such a way that it will just be submerged?
2. The specific gravity of rock used as concrete aggregate is often desirable to know. If a rock weighed 6.50 N in the air and 3.80 N submerged in water, what would be the specific gravity of the rock?
3. A piece of wood weighs 17.80 N in air and a piece of metal weighs 14.80 N in water. Together the two weighs 13.35 N in water. What is the specific gravity of the wood?
