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Why Do Objects Float?

Why Do Objects Float? . The Buoyant Force. Can you Float? Buoyant force: is an upward force that is exerted by a fluid on any object in the fluid. . What causes buoyant force? .

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Why Do Objects Float?

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  1. Why Do Objects Float?

  2. The Buoyant Force • Can you Float? • Buoyant force: is an upward force that is exerted by a fluid on any object in the fluid.

  3. What causes buoyant force? • When you float, the forces on you are balanced. Gravity pulls you downward and is balanced by a buoyant force pushing upward. Gravity Buoyancy

  4. Review of Lab! • Forcing acting on the bottom of an object in fluid is greater, this upward force is the buoyant force. • A buoyant force acts on all objects that are placed in fluid, whether they are floating or sinking

  5. Sinking and Floating • Why do stones sink and twigs float? • If the weight of an object is greater than the buoyant force it sinks • If the buoyant force is equal to the object’s weight, the forces are balanced and the object floats.

  6. Changing the Buoyant Force • Buoyant Force and Shape • The buoyant force depends on the shape of an object. • Curved hulls of large (heavy) ships have large contact areas with the water, the force on the hull is greater than the weight of the ship so it floats. • Buoyant Force DOES NOT change with Depth • Buoyant force does not change with the depth as the pressure is felt all around the object, just like Mr. Pascal said “pressure is felt equally”

  7. Archimedes Principal • Archimedes Principal states: the buoyant force on an object is equal to the weight of the fluid it displaces • Ice Cubes in a Glass of water • Ice dropped in a glass of full water will cause the water to “overflow” or “displace” from the glass • If you collect the water that overflows it will be equal to the buoyant force on the ice cube • The buoyant force or “weight” of the water displaced is equal to the weight of the ice cube

  8. Density • The density of a fluid or an object is the mass of the object divided by the volume it occupies • Density = Mass/Volume • D=M/V

  9. Sinking and Density • Remember the density of water is……………. • Anything greater thank the density of the water will sink

  10. Floating and Density • Wood Floats because it is less dense than the water. • Anything that is less dense than water will float

  11. Boats • Boats float because they are filled with air, the volume increases allowing it to float • Figure 18 on page 80

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