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Topic: 6: Fluids - Prepared by Shakil Raiman. 6.1 Density  Density is defined as mass per unit volume   Unit: Kg/m 3.

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Presentation on theme: "Topic: 6: Fluids - Prepared by Shakil Raiman. 6.1 Density  Density is defined as mass per unit volume   Unit: Kg/m 3."— Presentation transcript:

1 Topic: 6: Fluids - Prepared by Shakil Raiman

2 6.1 Density  Density is defined as mass per unit volume   Unit: Kg/m 3

3 6.2: Relative Density  It is defined as the ratio of density of an object to the density of a fluid.   It has no unit

4 6.3: Pressure  It is defined as force per unit area.   Unit: Nm -2 or Pa (Pascal)  Pressure in Liquid = h  g

5 6.4: Upthrust in Fluids  When an object is immersed in fluid, the upthrust is equals to the weight of the displaced fluid.  The upthrust is the difference between the force due to liquid pressure at the bottom surface and top surface of an object.  Unit: N

6 6.5: Flotation  An object will float in a fluid if the upthrust – that is, the weight of the fluid it displaces – is equals to its weight.

7 6.6: Moving Fluids –Streamline flow or laminar flow.  While fluid flows, if there is no mixing of layers or no vortices or no eddies are formed, this is called streamline flow or laminar flow.  Check on the board.

8 6.7: Moving Fluids –Turbulent flow  While fluid flows, if there is mixing of layers or vortices or eddies are formed, this is called turbulent flow.  Check on the board.

9 6.8: Viscosity  The viscosity of a fluid relates to its stickiness and thus to its resistance to flow.  Syrup and engine oil are very viscous.  Runny liquids such as water and petrol and all gasses have low viscosity.  For the same fluid, if temperature increases viscosity decreases.

10 6.9: Drag  The drag on an object moving in a fluid is the opposing force due to its stickiness with the fluid or viscosity of the fluid.  When a sphere of radius r, moves slowly through a fluid with velocity v, the viscous drag on it is stated by Stokes’ Law.  Viscous drag,  Where  = coefficient of viscosity.

11 6.10: Acceleration and Terminal Velocity  When a sphere is released and allowed to fall freely in a fluid, it is subjected to three forces:  its weight, W, the upthrust, U and viscous drag, F  For accelerating downward, W>U+F  For terminal velocity, W=U+F  For decelerating downward, W

12 6.11: Measuring viscosity using Stokes’ Law  By measuring the terminal velocity of a sphere falling through a fluid it is possible to determine the coefficient of viscosity of the fluid.  For a sphere of radius r and density  s falling through a fluid of density  f and viscosity  with a terminal velocity v, the equilibrium equation:  U+F=W


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