Pressure and Buoyancy 8th grade Science

Published on: **Mar 4, 2016**

- 1. Pressure Notes The fun never stops...
- 2. Pressure in a Fluid • Liquids and Gases can exert forces. – Examples: waves crashing, wind
- 3. Pressure in a Fluid • Liquids and Gases can exert forces. – Examples: waves crashing, wind • Liquids and Gases are fluids
- 4. Pressure in a Fluid • Liquids and Gases can exert forces. – Examples: waves crashing, wind • Liquids and Gases are fluids • Fluids exert force
- 5. Pressure in a Fluid (cont) Objects in a fluid experience a buoyant force resulting from the pressure exerted by the fluid.
- 6. Pressure in a Fluid (cont) Objects in a fluid experience a buoyant force because of the pressure of the fluid.
- 7. What is Pressure? • Pressure is the force per unit of area applied on the surface of an object.
- 8. What is Pressure? • Pressure is the force per unit of area applied on the surface of an object. • Pressure depends on the force applied, and the area of contact over which the force is applied.
- 9. Calculating Pressure 1 Pa = 1 N/m2 1 Pa is equal to the force of 1 Newton applied over an area of 1 m 2
- 10. Pressure and Fluid Height • For any fluid, pressure depends only on the height of the column of fluid above the surface.
- 11. Pressure and Fluid Height • For any fluid, pressure depends only on the height of the column of fluid above the surface. • Increasing the height of the column of fluid increases the pressure.
- 12. Pressure and Depth • Pressure increases with depth.
- 13. Pressure and Depth • Pressure increases with depth. • The water column pushing down becomes taller and heavier with increasing depth.
- 14. Pressure in All Directions • Fluids exert a pressure in all directions on an object. • The pressure is perpendicular to the surface of the object.
- 15. Atmospheric Pressure • Atmospheric pressure is the force exerted per unit area by air particles. • Atmospheric pressure decreases as elevation increases.
- 16. Atmospheric Pressure Crushing things: • http://www.youtube.com/watch?v=L2WDF1lu • http://www.youtube.com/watch?v =gG5YmkmfCpA • http://www.youtube.com/watch?v =Uy-SN5j1ogk • http://www.youtube.com/watch?v =2WJVHtF8GwI
- 17. Buoyant Force Buoyant force is the upward force on an object in a fluid exerted by the surrounding fluid.
- 18. Buoyant Force (cont) • Buoyant force is the result of increasing pressure at increasing depth. • Pressure on the top of the object is less than the pressure on the bottom of the object, resulting in an unbalanced force.
- 19. Buoyant Force and Depth • The pressure exerted by a fluid increases as depth increases. • The buoyant force remains constant on a submerged object.
- 20. Archimedes Principle • Archimedes’ principle, the buoyant force on an object is equal to the weight of the fluid the object displaces. • The buoyant force does not depend on the object’s density or weight.
- 21. Sinking and Floating • If the upward buoyant force is less than the object’s weight, the net force on the object is downward.
- 22. How Can Metal Ships Float? • Overall density of the ship is less than the density of water because a large volume of the ship is filled with air.
- 23. Floating and Sinking in the Atmosphere • Air produces a buoyant force. • Helium balloon’s weight is less than the buoyant force. • The density of the balloon is less than the density of the surrounding air.
- 24. Floating and Sinking in the Atmosphere • Hot-air balloons float when their weight is less than the weight of displaced air. • Heat from the burner heats the air particles and causes them to move farther apart. • The density of the balloon decreases and becomes less dense than the surrounding air.
- 25. Videos • • Mythbusters "Let's Talk Buoyancy" http://science.howstuffworks.com/6540-mythbusters-lets-talkbuoyancy-video.htm • • Mythbusters Lead balloon 5 min http://www.youtube.com/watch?v=HZSkM-QEeUg • • Mythbusters Barrel of Bricks http://www.youtube.com/watch?v=Vt230Pd1oSo • • Sulfur Hexafluoride Gas Boat float http://www.youtube.com/watch?v=ckaJs_u2U_A • • Mythbusters Sulfur Hexafluoride Boat float attempt http://www.youtube.com/watch?v=KReTvW7BTHQ