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- 1. Buoyancy & Flight
- 2. Review Newton’s Laws Explanation Summary First inertia Second When an object is acted on by an unbalanced force, it will accelerate in the direction of that force. Third action-reaction
- 3. Review <ul><li>What is pressure? </li></ul><ul><ul><li>Amount of force applied to a unit of area. </li></ul></ul><ul><li>What formula do we use to calculate pressure? </li></ul><ul><ul><li>P = F/A </li></ul></ul><ul><li>What units are used to measure pressure? </li></ul><ul><ul><li>pascals (Pa) </li></ul></ul><ul><li>What is Pascal’s Principle? </li></ul><ul><ul><li>A force applied to a fluid in a closed container will cause an increase in pressure, equally transmitted to all parts of the fluid. </li></ul></ul><ul><li>How does depth affect pressure? </li></ul><ul><ul><li>Pressure also increases with depth. </li></ul></ul>
- 4. Density <ul><li>Density : How much mass is contained in a certain volume. </li></ul><ul><li>Density = mass/volume or D = m v </li></ul><ul><ul><li>(Volume = length x width x depth) </li></ul></ul><ul><ul><li>Units for density: g/mL (or g/cm 3 or g/cc) </li></ul></ul><ul><ul><ul><li>(1 milliliter = 1 cubic centimeter) </li></ul></ul></ul>
- 5. Calculating Density <ul><li>What is the density of a metal if a 4 gram sample has a volume of 10 cm 3 ? </li></ul><ul><li>mass = 4 g </li></ul><ul><li>volume = 10 cm 3 </li></ul><ul><li>density = ? </li></ul><ul><li>D = 4g 10 cm 3 </li></ul><ul><li>density = 0.4 g/cm 3 </li></ul><ul><li>D = 8 g 10 cm 3 </li></ul><ul><li>density = 0.8 g/cm 3 </li></ul>D = m/v 4 g 8 g
- 6. Buoyancy <ul><li>Pressure in a fluid is exerted in all directions. </li></ul><ul><li>Pressure increases with depth. </li></ul><ul><li>What other forces act on a submerged object? </li></ul><ul><li>Gravity! </li></ul><ul><li>What affects the amount of gravitational force on an object? </li></ul><ul><li>Mass! </li></ul>F g F g
- 7. Archimedes’ principle <ul><li>Archimedes’ Principle : the buoyant force on an object is equal to the weight of the fluid displaced by the object. </li></ul><ul><ul><li>Buoyant force: the force that a fluid exerts on an object (upthrust) </li></ul></ul><ul><ul><ul><li>acts in an upward direction against gravity </li></ul></ul></ul><ul><ul><ul><li>makes objects feel lighter </li></ul></ul></ul>
- 8. Density and Buoyancy <ul><li>Water has a density of 1 g/mL at 25 degrees Celsius (temperature affects density because it changes volume) </li></ul><ul><ul><li>This means 1 mL of water has a mass of 1 gram </li></ul></ul><ul><ul><li>Objects with densities less than 1g/mL will float. </li></ul></ul><ul><ul><li>Objects with densities greater than 1g/mL will sink. </li></ul></ul>
- 9. Bernoulli’s Principle <ul><li>Bernoulli’s principle: The pressure exerted by a moving fluid is less than the pressure of the surrounding fluid. </li></ul><ul><ul><li>Daniel Bernoulli was a mathematician who studied fluid mechanics (the motion of fluids). </li></ul></ul><ul><ul><li>He found that the faster a fluid moves the less pressure it exerts . </li></ul></ul>
- 11. Prairie Dog Burrows <ul><li>Air is forced up and over the raised mound, causing an area of low pressure. </li></ul><ul><li>Fresh air flows through since fluids of higher pressure always move towards low pressure . </li></ul><ul><ul><li>Wouldn't work if both openings were level. </li></ul></ul>
- 12. <ul><li>How would Bernouli's Principle help an architect design a weather-exposed house in the windy Columbia River Gorge? </li></ul>
- 13. How Airfoils Create Lift <ul><li>The air makes it over top and bottom in the same amount of time. (Remember speed=distance/time?) </li></ul><ul><ul><li>Air moves faster to get over the top curve. </li></ul></ul><ul><li>Faster fluids have less pressure (Bernoulli's principle) </li></ul><ul><li>Slower air under wing pushes with greater force than the air above it, creating “lift” </li></ul><ul><li>If the flying apparatus goes fast enough, the "lift" will be great enough to overcome the pull of gravity. </li></ul>
- 14. Wing Design

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