Lab 12: Archimedes’ Principle with Conclusions, Lab Reports of Physics

Download Lab 12: Archimedes’ Principle with Conclusions and more Lab Reports Physics in PDF only on Docsity! Lab 12: Archimedes’ Principle Equipment: Plastic beakers, small metal beakers, beakers with spouts, density sample cube sets, digital scales, force probes, 1000g mass, calipers, rubber stoppers for force probes. In this experiment you will use Archimedes’ Principle to determine the volume and density of several cubes made of different materials, and will verify Archimedes’ Principle by weighing the water displaced by an object. Introduction To understand how we are going to determine the density of an object using Archimedes’ Principle there are a few preliminary ideas to consider: 1. The pressure in a fluid of density ρ at a depth d is given by: P = ρgd (1) 2. Objects seem to have less weight when submerged in liquids due to the upward force of the liquid surrounding them. The buoyant force acting on a submerged object is due to the difference in pressure above and below the object (since its top and bottom are at different depths). The buoyant force is also equal to the weight of the object in the air minus the weight of the object in the fluid: FB = Win air – Win fluid (2) 3. Archimedes’ Principle: The buoyant force on a submerged body equals the weight of the fluid it displaces: FB = ρfluid Vg (3) Setting equations (2) and (3) equal to each other (because they both describe the buoyant force), we can solve for the volume of the object. This is the same as the volume of the displaced fluid: Win air – Win fluid = ρfluid Vg V= (Win air – Win fluid ) / ρfluid g (4) This relationship is very useful if you want to determine the volume of an object with an odd shape. All you have to do is weigh the object in a fluid of known density (we will use water) and then weigh it in air to determine the buoyant force and thus its volume. Once we know the volume of an object, we can measure the mass and thus also determine its density. ρobject = m/V = m/ [(Win air – Win fluid ) / ρfluid g] (5) Calibrating the force probe 1. Connect the force probe to the “CH 1” port on the LabPro interface, connect the LabPro to the power cord, and open Logger Pro. 2. Click the small green icon for “Set up Sensors” (or select this option from the Experiment menu), and under the CH 1 menu select Force -> Dual Range Force. A small picture of the force probe should appear in the CH 1 box. 3. Go back to the experiment menu and select Calibrate -> LabPro: 1 CH1: Dual Range Force. A “Sensor Settings” window should appear. Click the “Calibrate Now” button. 4. Holding the force probe upright with nothing hanging from the hook, enter 0 into the “Reading 1” box and click “Keep”. 5. Now hang the 1000g mass from the hook, wait a few seconds, then enter 9.8 in the “Reading 2” box and click “Keep”. This will set the force probe to treat the weight of a 1kg mass as 9.8N. 6. Close the Sensor Settings window, and check your calibration by hitting the Collect button. Logger Pro should be collecting around 9.8 N of force while the 1000g mass is hanging from it. You are now ready to take force readings! Procedure 1. Use the calipers to measure the dimensions and determine the volume of each cube. Include in your lab report an example of how you calculated the volume of one of the cubes (note: they may not be perfect cubes!). 2. Fill your large plastic beaker mostly full with water (leave some space for the cubes to fit without spilling the water over the edge of the beaker for now). 3. For each of the cubes in the box measure its mass with the digital scale, then measure the weight in air and weight in water using the force probe. You will need to use the rubber stopper attachment on the force probe instead of the hook to push the lightweight cubes below the surface of the water in order to get an accurate reading, and this might take a little practice. 4. Now take the small metal beaker and use the digital scale to measure its mass. 5. Place the small metal beaker under the spout of the larger beaker, and fill the larger beaker with just enough water to reach the spout. If any spills out into the small beaker, empty it out. 6. Carefully place the object in the water and allow the excess water to spill out the spout and into the small beaker. Measure the mass of the small beaker with the displaced water. Subtract off the mass of the beaker from step 3, and record the mass of the displaced water in your spreadsheet for this cube. 7. Repeat steps 3-6 for the rest of the cubes. Now you have the mass of the water displaced by each cube. 8. Calculate the volume for each of your objects using the data in your data table (use the density of water = 1 g/cm3), and make sure the volumes are in cm3. Show an example calculation in your lab report, and record your results in your data table. 9. Using the mass data from step 3 and volume calculations from step 8, calculate the density of each of your cubes.