Buoyant Force and Archimedes Principle Pre-Lab Questions Draw a free body diagram of a hanging mass before it is submerged in water. Make sure to label your forces. Draw a free body diagram of a hanging mass after it is submerged in water. Make sure to label your forces. Which force is the force you measure with the spring scale? Apply Newton’s second law to your free body diagram in Pre-Lab Question 2 to solve for the magnitude of the buoyant force. A wooden crate, made from wood with density ρw, is floating on a liquid with density ρl. Formulate a general equation for the depth the crate is submerged, h, if the crate has a length, L, width, W, and height, H. Write your equation in variable form. Solve for the depth the crate is submerged if ρw = 670 kg/m3, ρl = 1,100 kg/m3. L = 10 m, W = 7.0 m, and H = 5.0 m. If the crate is submerged under the water, Derive a general equation for the acceleration of the box after it is released. Show your work. Determine the acceleration of the wooden crate for the values given in Pre-Lab Question 4. Show your work. Experiment 1: Effects of Density Data Sheet Post-Lab Questions Sketch and label what the arrangement of objects and liquids in the beaker. Rank the liquids and solids in order of least to most dense and use your results to explain you reasoning. Which of the solid materials used in this experiment would make the best boat? Why? Would it be easier to design a boat in a world with oceans of maple syrup than oceans of saltwater? What property of maple syrup might prevent boats from traveling in it very effectively compared with in water? Experiment 2: Buoyant Force and Floating Data Sheet Table 1. Number of Washers a Clay Boat Can Hold before Sinking Type of Liquid Number of Washers Plain Water Salt Water Post-Lab Questions What did you observe when you placed the ball of clay into the beaker? What were characteristics of the boat design that floated the best? Use Archimedes’ Principle to explain why these design characteristics cause the boat to float, and the clay ball to sink. If your clay boat weighs .005 kg and is floating, what is the upward force the water is exerting on the boat? How could you improve your boat design to increase the buoyant force without using more clay? In the second part of the experiment, does the boat hold more weight in the regular water or the salt mixture? What does this say about the relative densities of salt water and plain water? How much water does an object have to displace before it will float? Experiment 3: Buoyant Force and Archimedes Principle Data Sheet Table 2. Dimensions of 250g Hanging Mass Hexagonal Base Edge (cm) Base Diameter (cm) (cylindrical mass) Height (cm) Table 3. 250 g Hanging Mass Buoyancy Data Object Weight in Air (N) Weight in Water (N) Buoyancy Force (N) Volume Displaced (mL) 250 g Hanging Mass Rubber Stopper Post-Lab Questions What happens to the apparent weight when the objects are submerged in water? Use the value of the buoyant force to calculate an experimental value of the volume of the 250 g mass in kg/m3 (Fb = ρLVD g). The density of water is approximately 1,000 kg/m3. Show your work. Use the measured dimensions of the 250 g mass to calculate the volume of the mass based on its shape. Show your work. Determine the percent difference between the measured volume of the 250 g mass and the value calculated from the buoyant force measurement. Show your work. Using the fact that 1 mL = 1 x 10-6 m3, compare the volume of the displaced water to the calculated volume of the mass from Post-Lab Question 3 with a percent error calculation. Show your work. Are the three experimental values of the volume of the 250 g mass (from Archimedes’ Principle) larger or smaller than the calculated value using the caliper measurements? Why? Which of the three values for volume is more accurate? Which of the two experimental volumes are more accurate? Explain. Does the data support Archimedes’ Principle? Why or why not? Identify two possible sources of error in the experiment. How could the procedure be revised to remove these potential errors? ©eScience Labs, 2014