Chapter 5 – The Properties of Fluids

1. Key Ideas Knowledge of the properties of fluids is important in technology An object immersed in a fluid will experience pressure Forces can be transferred through confined fluids Pressure, temperature, and volume of a fluid affect each other Machines and other devices that use fluids can make work and movement easier Chapter 5 – The Properties of Fluids

2. 5.4 – Fluids Under Pressure

3. Pressure • PRESSURE – is the amount of force per unit area • Use the following formula to determine pressure • Pressure = force/area –or – p=F/A • *Remember* Force is measured in Newtons (N) and area is measured in cm2 or m2 • As you can see from the above formula – the larger the area the force is applied to, the lower the pressure will be

4. Pressure • Can you explain how these snowshoes help this person travel across the snow?

5. Pressure – Sample Problem

6. Pressure • Pressure is measured in pascals • Pascal (Pa)– the unit of measure for pressure; equivalent to one Newton per square metre (N/m2) • A pascal is a relatively small force so we use kilopascals (kPa) • 1 kPa = 1000 Pa • So 1kPA = 1000 (N/m2)

7. Atmospheric Pressure Atmospheric Pressure– the weight of the air pushing down on itself and on the Earth's surface The average pressure of Earth’s atmosphere is about 100 kPa – this will change with weather conditions and elevation http://www.goorulearning.org/gooru/index.g#!/r/7fc46ad1-4eda-44d5-8ad9-f7d499de2d51 http://www.goorulearning.org/gooru/index.g#!/r/3f948365-f0c6-4e89-b52e-b68f623ce8fa

8. How is temperature related to Pressure? Now, here's where it all comes together. Since the atmosphere is warmed from the ground up, and since the air is at its most dense near the surface of the earth, the air near the surface is going to be able to retain much more heat than the air at higher elevations due to the increased amounts of air molecules; higher elevations have fewer air molecules and consequently can't retain as much heat. So, even though you would be much closer to the sun if you were standing on top of a mountain, the air temperature would be considerably less than it would be at sea level.

9. Atmospheric Pressure

10. 5.5 – Pressure in Confined Fluids

11. Pressure in Confined Fluids • A confined fluid means that a fluid can move around but cannot leave the system • Blood is a confined fluid (unless you get cut) and air in a tire is confined

12. Pressure in Confined Fluids • There are two types of systems that use confined fluids to transmit forces from one location to another • Hydraulic System– is a confined, pressurized system that uses moving liquids. • Pneumatic System– is a confined, pressurized system that uses moving air or other gases.

13. Pressure in Confined Fluids

14. Pressure and Forces in a Hydraulic System • From our syringe exercise we learned: • both plungers moved the same distance, but in opposite directions • one plunger moved down and the other plunger moved up • the force pushing down on one plunger was the same as the force pushing up on the other plunger • To make a hydraulic system more effective you need to change the relative sizes of the cylinders

15. Pressure and Forces in a Hydraulic System • The force on the smaller cylinder is multiplied in the larger cylinder. • The amount that the force is multiplied by is determined by the ratio of the areas of the larger and smaller pistons. • For example, if the area of the larger piston is nine times larger than the area of the smaller piston, the force on the larger cylinder is nine times larger than the force on the smaller cylinder. • To do the same amount of work, however, the smaller piston must move a greater distance

17. Solution

18. Practice

19. Using The Kinetic Molecular Theory • Using the KMT we know that the spaces between gases are much greater than the spaces between liquids • Gases must be compressed before they can transfer force • Compression- action where an external force pushes particles together reducing volume • Compressible- characteristic of a substance where its volume can be reduced by external pressure **If enough pressure is added or taken away a change of state can occur**

20. 5.8 – Fluid Power at Work

21. Fluid Power @ Work Uses for Fluids • To Entertain Us • Rescue • Training • Construction

22. Entertain Us • The movie Jurassic Park used a hydraulic system. Each part was the dinosaur was connected by remote control. • Roller coasters are moved using puenmatic system compressed air!

23. For Rescue • Jaws of life is a rescue tool that pries open car doors in the case of an accident. It uses fire resistant fluids in the hydraulic system. Why fire resistant?

24. Training Use • Hydraulic system help train pilots, driving and ship captain cause we can recreate dangerous movements while operating this machinery.

25. Construction • TBM (Tunnel Building Machine) builds subway tunnels. It works by hydraulic motors rotating the cutting head while the hydraulic cylinders pushes the machine forward

26. Homework • Tomorrow please bring a regular size water/pop bottle for 5.6 lab. • Please read the lab for more details page 156 • Chapter 5 quiz Monday