Archimedes’ Principle and Specific Density

2365 Words Mar 27th, 2012 10 Pages
Physics 141 Archimedes --1

GOAL: To investigate buoyant force and Archimedes’ principle. To measure the specific density of several materials. INTRODUCTION: Try pushing down on a basketball in water and you feel the buoyant force that makes the ball float. As more of the ball is pushed beneath the water, the upward force becomes greater. One could make a first guess (Hypothesis #1) that the buoyant force increases with the submerged volume of the object. A more mathematical guess (Hypothesis #2) might be that the upward or buoyant force, B, is proportional to the submerged volume, Vsub, of the object. feathers, is in fact a statement that the density of lead is greater than the density of
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METHOD I. (Spring Scale Method) Using the spring scale, measure the buoyant force as a function of volume submerged for the wooden block (use eq.6). This is a test of Hypotheses # 1 and 2. To measure the submerged volume, consider placing a piece of tape marked with distances along the height of the block. Compare this volume to the increase in volume in the container as indicated by the rise in the water level (Hypothesis #3). Estimate the specific density of the wooden block. Consider using the weights from the mass set to extend this measurement into the experimental region where the buoyant force exceeds the weight of the block.

Figure 2 The pan balance method for measuring the buoyant force and specific density. METHOD III. (Graduated Cylinder Method) Determine the mass of the empty graduated cylinder and an average mass for the washers. Place about 10 washers in the graduated cylinder, and carefully place the cylinder in the beaker which is about 2/3 full of water. This initial loading with washers should insure that the cylinder floats upright, if not add more washers. Be careful not to have air bubbles under the base of the cylinder. Record the number of washers and volume markings on the graduated cylinder at the waterline as the cylinder floats. Add a washer, and record these values again. Repeat this process of adding washer and recording up to the point of sinking the cylinder. Plot volume marking vs number of washers


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