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Fluids and Pressure Chapter 3 Fluids Any material that can flow and take the shape of its container *Fluids include gases and liquids All Fluids Exert Pressure Remember Boyles Law Calculating Pressure Pressure = Force / Area Area = Force / Pressure SI unit for pressure is pascal Written 1 Pa Remember – Force = Newton – Area = m2 Math Break Turn to Page 62 1. Find the pressure exerted by 3,000N crate with an area of 2m2 Hint: Pressure = Force / Area Solution Force = 3000 N Area = 2 m2 Pressure = ? Pressure = 3000N / 2 m2 = 1,500 Pa Question 2 Find the weight of a rock with an area of 10 m2 that exerts a pressure of 250 Pa Solution Area = 10 m2 Force = ? Pressure = 250 Pa Force = 250 Pa x 10 m2 = 2,500 N Atmospheric Pressure The small amount of pressure (weight) caused by the Atmosphere Approx: 101,300 N or 101,300 Pa http://www.wfu.edu/physics/demolabs/dem os/avimov/fluids/marshmallow_man/marsh mallow_man.MPG Example Water Pressure Increases with depth Is denser than air so it exerts more pressure Fluids Flow from High Pressure to Low Pressure Think about drinking straws Pascal's Principle Pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid, as well as to the walls of the container. http://webphysics.davidson.edu/physlet_re sources/bu_semester1/c23_pressure_pas cal.html http://www.wfu.edu/physics/demolabs/dem os/2/2b/2B2042.html Automobile Hydraulic Lift Quick Lab Page. 66 Turn in question 6 Page 64 Questions 1-3 Buoyant Forces The upper force that fluids exert on an object Law of Archimedes: The buoyant force is equal to the weight of the replaced liquid or gas. http://www.youtube.com/watch?v=vJ36urazDu4 Weight vs Buoyant Force Use figure 10 on page 69 Draw 3 objects not listed in picture that would Sink, Float and Float on the surface of water Draw forces using arrows The Mystery of Floating Steel *Remember D= m / v How Fish Float The swim bladder allows fish to change there density This allows them to float at different depths How does increasing volume affect the fishes floating? Page 71 Quick Lab: Ship-Shape Turn in Question 3 Due Before the end of Class Homework Page 72 (1-3) Homework Page 72 Question (1-4) Bernoulli’s Principal As speed of a moving fluid increases, it’s pressure decreases Swiss Mathematician Example Shower Curtain Page 73 Quick Lab Turn in a Diagram of results and Question 3 Label High and low pressure Page 77 (1-4) Quick Lab b Hold one end of a small sheet of paper in both hands. Keep the held edge horizontal while the other end sags under its own weight. Blow steadily over the top of this horizontal edge. Terms To Know The upward force that pushes against gravity The fluid force the opposes motion of the object The forward force produced by fling object (planes engine) Wings are Not a Requirement for Flight Curveball exhibit Bernoulli’s Principal Biplane Airship Jet Glider Pick any two of the following aircrafts and compare and contrast them in terms of lift, drag, thrust and gravity? What are the characteristics of each that allow them to fly? Short Review Fluids in Pressure – Pressure in Atmosphere – Pressure under water – Altitude and Pressure Buoyant Forces – Sinking, Floating, Buoying up – Archimedes Principle – Density Bernoulli’s Principal – Fluid speed effect pressure How? – Airplane Terms Study Guide Time Test March 10th Lets Make A’s