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General Physics

General Physics. Chapter 2: Fluids Instructor: Sujood alazzam. CHAPTER OUTLINE. Density Pressure Flow of ideal liquid Viscosity Diffusion Surface Tension. 2.1 Fluid. Fluid = matter that flows under external forces ≡ liquid & gas. 2.2 Density & Pressure.

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General Physics

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  1. General Physics Chapter 2: Fluids Instructor: Sujood alazzam

  2. CHAPTER OUTLINE • Density • Pressure • Flow of ideal liquid • Viscosity • Diffusion • Surface Tension

  3. 2.1 Fluid • Fluid = matter that flows under external forces ≡ liquid & gas.

  4. 2.2 Density & Pressure • Which weighs more:- A kilogram of feathers or a kilogram of iron?

  5. What is Density? If you take the same volume of different substances, then they will weigh different amounts. Density is the Mass per unit Volume Wood Water Iron 1 cm3 1 cm3 1 cm3 IRON 0.50 g 1.00 g 8.00 g Q) Which has the greatest mass and therefore the most dense?

  6. m  V Density Equation: g or kg Mass Density = Volume gcm-3 or kgm-3 cm3 or kg3 Example: Q) Liquid water has a density of 1000kgm-3, while ice has density of 920kgm-3. Calculate the volume occupied by 0.25kg of each. V= m = 0.25 = 0.000250m3  1000 V = m = 0.25 = 0.000272m3  920

  7. DENSITY OF A REGULAR SOLID • Find the Mass of the solid on a balance. • Measure the three lengths and calculate the Volume. (i.e. V = l x w x h ) • Calculate the Density. m = 240 g 2.0 cm = m = 240 =10.0 g/cm3 V 24 3.0 cm 4.0 cm

  8. Example 1: A small cube of iron is observed under a microscope. The edge of the cube is 5.00 * 10-6 cm long. Find the mass of the cube. its density is 7.86 g/cm3.

  9. 2.3.1 Pressure Pressure = normal force per unit area A n F • Pressure is a scalar. • The pressure at a point in a fluid is the magnitude of the radial force per unit area acting on a fluid point at that position. Fluid point

  10. 2.3.2 Measuring Pressure Barometer = device for measuring atmospheric pressure vacuum inside tube:

  11. Manometer Manometer = U-shaped tube filled with liquid to measure pressure differences. equal p Gauge pressure = excess pressure above atmospheric. Used in tires, sport equipments, etc. E.g., tire gauge pressure = 30 psi  tire pressure = 44.7 psi Pascal’s law: An external pressure applied to a fluid in a closed vessel is uniformly transmitted throughout the fluid.

  12. Example 2: Hydraulic Lift In a hydraulic lift, a large piston supports a car. The total mass of car & piston is 3200 kg. What force must be applied to the smaller piston to support the car? Pascal’s law 

  13. Example 3:

  14. Example 4:

  15. 2.3 Archimedes’ Principle & Buoyancy Buoyancy force: Upward force felt by an object in a fluid. fluid element in equilibrium Archimedes’ Principle: The buoyancy force on an object is equal to the weight of the fluid it displaces.

  16. Example 5:

  17. Example 6: Working under Water To set up a raft, you need to move a 60-kg block of concrete on the lake bottom. What’s the apparent weight of the block as you lift it underwater? The density of concrete is 2200 kg / m3 .

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