Experiment 2 Buoyant Force and Floating Have you ever wondered why you feel weightless in water If you have spent enough time in the pool you will know that it is possible to lift heavy objects underwater like a person that would require much more effort to lift on land This phenomenon is due to the effect of the buoyant force that acts on solids submerged in liquids In this experiment you will explore the science behind why objects seem lighter in water and will explain this reduction in weight using Archimedes Principle You will also examine buoyancy in a solution of salt water and compare it to that in plain water and will explain your observations in terms of density Materials 1 250 mL Beaker 1 100 mL Graduated Cylinder Measuring Spoon Stick Modeling Clay Popsicle Stick 5 tsp Sodium Chloride Salt NaCl 15 Washers Paper Towels Water You Must Provide Procedure 1 Use the graduated cylinder to measure and pour 150 mL of water into a 250 mL beaker 2 Take a stick of modeling clay and divide it into two equal pieces so that the masses are equal 3 Roll one piece into a ball and place it in the beaker Observe the buoyancy of the ball Record your observations in Post Lab Question 1 4 Remove the ball from the beaker 5 Design a shape for a clay boat so that the boat will float 6 Use the remaining clay to form your boat design Remember you want the buoyant force to be large along with a shape that won t tip over 7 Place your boat in the beaker and observe what happens If your boat doesn t float try out different shapes until you are successful Use these observations to answer Post Lab Question 2 8 Once you have designed and built a boat that floats add metal washers to the boat one by one Record how many washers you can add before the boat sinks in Table 1 9 Remove the boat and washers mix five teaspoons of salt into your beaker stir well with a popsicle stick to ensure the salt is even dissolved in the water and repeat Step 8 2014 eScience Labs LLC All Rights Reserved Table 1 Number of Washers a Clay Boat Can Hold Before Sinking Type of Liquid Number of Washers Plain Water 5 Salt Water 7 Post Lab Questions 1 What did you observe when you placed the ball of clay into the beaker 2 What were characteristics of the boat design that floated the best Explain why this works and the clay ball fails to float using Archimedes Principle 3 How much water does an object have to displace before it will float 4 If your clay boat weighs 005 kg and is floating what is the upward force the water is exerting on the boat 5 How could you improve your boat design to increase the buoyant force without using more clay 2014 eScience Labs LLC All Rights Reserved 6 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 2014 eScience Labs LLC All Rights Reserved
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