F5 - Archimedes' Principle Prelab questions Student Name: Lab Week: Student Number: Lab Day and Start Time: Question 1 Draw free body diagrams of a sample (a) suspended from a string in air, (b) suspended from a string while fully submerged in water, and (c) partially submerged (floating) in a fluid. Free body diagram (a) 0.5 0 Free body diagram (b) 0.5 Free body diagram (c) 0.5 Question 2 If the density of the floating object is Pobject and the density of the fluid is Pfluid, write an expression for Pobject in terms of Pfluid, the total volume of the object (Vtotal) and the volume of the object that is submerged (Vsubmerged). Understanding of governing equations 0.5 0 Question 3 Identify three potential risks that are associated with this practical/laboratory. 2. 3. Identification of potential risks in the lab 1 0.5 0Risk Assessment Risk assessment is extremely important in engineering. It is your job as engineers to identify and understand the risks present and to suggest measures to prevent harm from happening. Risks are assessed using the matrix below. The two main criteria used are likelihood of occurrences and severity of consequences. Risks are mitigated through a hierarchy of controls. Consequences Likelihood Insignificant Minor Moderate Major Catastrophic Almost Certain - Expected in most Low + Moderate + Hig Very High xtreme circumstances Likely - Will probably occur in most Low - Moderate - Moderate + High Very High circumstances Possible - Might occur at some time legligible Low - Moderate - Moderate + High Unlikely - Could occur at some time Negligible LOW - Low + Moderate - Moderate + Rare - May occur only in exceptional Negligible Negligible Negligible Low - Low + circumstances Consequences How severely could it hurt someone/cause damage? Catastrophic Death or large number of serious injuries, env onmental disaster, huge cost Major Serious injury, extensive injuries, severe environmental damage, major cost Moderate Medical treatment required, containe d environmental impact, high cost Mino First aid treatment required, some environmental and/or financial impact Insignificant No injuries, low financial/environmental impact Risk score What should I do? Extreme Immediate action required Very High Senior management attention required High Action plan required, senior management attention needed Moderate Specific monitoring or procedures required, management responsibility must be specified LOW Manage through routine procedures Negligible Accept the risk effective Hierarchy of Controls Elimination Physically remove the hazard Substitution Replace the hazard Engineering Isolate people Controls from the hazard Administrative Change the way Controls | people work PPE Protect the worker with Personal Protective Equipment Least affective Procedure Part A - Weighing the samples 1. Zero the electronic balance and place a sample on it. Record the mass in the "Mass of samples" table on your proforma. 2. Repeat Step 1 for all of the samples listed in the table.F5 - Archimedes' Principle Objective To use Archimedes' principle to calculate the densities of a range of sample materials. Equipment laptop + PASCO Capstone digital measuring balance brass cylinder software Pasco force sensor displacement can aluminium cylinder retort stand beaker irregular aluminium sample digital callipers measuring cylinder set of cast iron masses Theory When an object is submerged in a fluid, the fluid exerts a buoyant force FB on the object which is equal to the weight of the fluid displaced by the object. As a result of this buoyant force, the object's apparent weight in the fluid will be less than its weight in air. apparent weight = weight - buoyant force W' = W-FB Here, W = mobjectg and FB = Mfluidg = Pfluid Vfluidg where mobject represent the mass of the object (kg), Pfluid represents the density of the fluid (m'/kg), Vfluid represents the volume of the displaced fluid (m3) and g is the acceleration due to gravity (m/s2). Experimental error A way to quantify experimental error is by comparing an experimental result with a published value. This can be done using the following equation: % variation Pexperimental - Ppublished -x 100% Ppublished Here, Pexperimental will be the Pcallipers, Pdisplaced and Pforce sensor that you will calculate and record on your proforma. The published densities of the materials/fluid used are: substance density, Ppublished (kg/m3) [1] brass 3470 aluminium 2700 cast iron 7150 water 1000Data analysis 1. Calculate the density of the sample from the data collected using your callipers and the mass measurement and record it in the \"Density determined using vernier callipers\" table. Calculate the density ofthe sample from the data collected using the water displacement measurements and mass measurement and record it in the \"Density determined using a displacement can\" table on your proforma. Calculate the volumes of water displaced by the samples in the "Density determined using the buoyant force\" table and, using the corresponding mass measurements, calculate the densities ofthe samples and record them in the same table. Using the data recorded in the \"Density of cast iron\" table, plot a graph of mass vs volume and use it to calculate the density of the cast iron masses. Calculate the density of the wooden block from the data collected using your callipers and the mass measurement and record it in the \"Density of a wooden block\" table. Using the data recorded in the \"Density ofa oating wooden block\" table, calculate the density of the wooden block and record it in the table. References Shackellbrd, .I. F. (2016) C RC materials scriencre and engineering handbook. Fourth edition. Boczl Raton, Florida: CRC Press, an imprint ofTaylor & Francis Group. Part B Determining the volume of samples 1 . Use vernier callipers to measure the diameters and lengths of the cylindrical samples and record these measurements in the \"Density determined using vernier callipers\" table on your proforma. Fill the displacement can until water ows from the spout and then wait for the flow to stop. Place an empty beaker under the spout to collect the overflow and then carefully lower the sample into the water. Once the water has stopped owing into the beaker, weigh the collected displaced water and record it in the \"Density determined using a displacement can\" table on your proforma. Repeat Steps 2-4 for all of the samples listed in the \"Density determined using a displacement can\" table on your proforma. Part C Measuring the buoyant force 1. 2. With nothing hanging from the hook, zero the force sensor. Hang the string that is attached to the aluminum cylinder from the hook that is attached to the force sensor so that the sample is suspended in the air and record the weight in the \"Density determined using the buoyant force" table on your proforma. Move the beaker containing water under the force sensor and completely submerge the sample, while ensuring that it doesn't touch the bottom or sides of the beaker. Record this apparent weight in the same table. Repeat for the other samples listed in the table, ensuring that the force sensor reads zero before attaching the next sample. Part D Graphical determination of density Using Steps 1-3 from Part C. record the mass, weight and apparent weight ofa range of cast iron (black) masses that are found in the blue tray in the \"Density of cast iron\" table on your proforma. Part E Density of a wooden block 1 . Zero the electronic balance and place the wooden block on it. Record the mass in the \"Density ofa wooden block\" table on your proforma. Using the digital vernier callipers, measure the dimensions of the wooden block and record them in the same table. The card on the bench in front of you shows images of the wooden block oating in water and sitting on a bench. Use the grids in the images to determine the fraction of the wooden block that is submerged and record it in the \"Density ofa oating wooden block\" table