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Viscosity PowerPoint Presentation

Viscosity

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Viscosity

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  1. Viscosity

  2. Fluid Resistance • An object moving through or on a fluid meets resistance. • Force causes the fluid to move. • The velocity is proportional to the force. F vx

  3. Velocity Gradient • The resistance tends to keep the fluid in place. • Law of inertia • The fluid moves most near the object and least farther away. • This is a velocity gradient. F vx y

  4. Law of Viscosity • Newton combined these two proportionalities. • This is the law of viscosity. • A is the area of the solid sliding on the fluid • The constant h is the dynamic viscosity and depends on the type of fluid. F vx y

  5. Flow in a tube is affected by sides in all directions. The relationship between velocity and distance is The total volume flow rate is Poiseuille’s Law r P1 vx P2 L

  6. Drag Force • Objects falling through a fluid reach terminal velocity. • For low speeds this is due to viscocity. • Stokes’s Law describes the drag force. Fd Fb Fg

  7. Surface Tension • Liquid molecules attract each other. • At the surface this force is the surface tension. • Force per length parallel to the surface. • Constant for different liquids insect leg on water next