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Learn about buoyancy, forces, and shapes affecting floating objects. Explore Archimedes' Principle and submarine mechanics. Hands-on experiments and discussions in Oceanography class.
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Oceanography Mrs. Brostrom October 11, 2013 IOTPOLYENGINEERING SP-2 SeaPerch Buoyancy Lesson
Supplies Needed • 1’x1’ alum foil • Weights • Water tubs • Graduated cylinders • 12 oz (or smaller) cups • 160 g sand for each team
1. Using the tub of water and the piece of aluminum foil, determine what makes an object float: Come up with 2 different floating boat shapes. How much mass can each hold? IOTPOLYENGINEERING SP-2 DRILL What is more relevant to keep objects floating: Weight or Shape
What are the forces acting on the iceberg below? Weight and Buoyancy IOTPOLYENGINEERING SP-2 BUOYANCY Force of Gravity Buoyancy = Weight
What is weight? The downward force of gravity acting on an object What is buoyancy? Buoyancy is the upward force that keeps objects afloat IOTPOLYENGINEERING SP-2 BUOYANCY Force of Gravity = Weight Buoyancy
What causes buoyancy? Archimedes’ Principle: An object is buoyed up by a force equal to the weight of the fluid displaced by the object. Buoyancy = Volumeobject x densityfluid B = (Vobject) x (rfluid) IOTPOLYENGINEERING SP-2 BUOYANCY
What is the volume of the plastic cup you were given at the beginning of class? What is the density of water? BUOYANCY LAB IOTPOLYENGINEERING SP-2 Volume = 12 oz = 355 mL rwater = 1 g/mL
If the cup were nearly submerged in water, what is the buoyancy force acting on it? B = (Vobject) x (rfluid) = (355mL) x (1 g/mL) B = 355 grams Why, then, does the cup float? The weight of the displaced water is greater than the weight of the cup. BUOYANCY LAB
How much weight of sand will it take to overcome the buoyancy force and sink the cup? Test this theory: There are about 160 grams of sand in the second cup you have. Add sand until the cup begins to sink. DO NOT let water infiltrate the sand. IOTPOLYENGINEERING SP-2 BUOYANCY LAB 355 grams
How do submarines use the principle of buoyancy to submerge and re-surface? This yellow submarine displaces so much water that its own weight is not great enough to have it sink in the ocean. How does it sink? IOTPOLYENGINEERING SP-2 Submarines
A valve opens and tanks in the submarine fill with water. The added water increases the weight of the submarine and it sinks. These tanks are called ballast tanks and the water/weight it picks up is called ballast. Submarines Weight < Buoyancy FLOATS Weight > Buoyancy SINKS
How does the submarine then rise back to the surface? It uses compressed air from tanks on board to force the ballast water back out, leaving only air. The buoyancy force then becomes greater than the weight, and the submarine rises. Submarines IOTPOLYENGINEERING SP-2 Weight < Buoyancy FLOATS Weight > Buoyancy SINKS
What is buoyancy? Which matters most; weight or shape? How do submarine sink and rise? IOTPOLYENGINEERING SP-2 Let’s Review