28: Hydrostatics, Archimedes' Principle, and Fluid Dynamics

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Topics covered: Concepts covered in this lecture include Hydrostatics, Archimedes' Principle, Fluid Dynamics, What makes your Boat Float?, and Bernoulli's Equation.

Instructor/speaker: Prof. Walter Lewin

Date recorded: November 17, 1999

Video Index

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  • Archimedes' Principle
    The buoyant force on an immersed body is shown to equal the weight of the displaced fluid (Archimedes' Principle). Such weight measurements can be used to determine the average density of irregular objects, and also to estimate body fat in people.

  • Floating Objects
    Most of an iceberg is submerged because its density is only a little less than the density of water. Boats float, rocks sink. Professor Lewin poses another brain teaser.

  • Stability of Floating Objects
    The center of mass of a floating object should be below the center of mass of the displaced fluid for stability; this is an important ship design concept.

  • Balloons
    The buoyant force of air on a balloon is discussed. It is demonstrated how a balloon and a pendulum behave in accelerated, closed containers.

  • Fluid Dynamics, Bernoulli's Equation
    Bernoulli's equation is presented as the conservation of energy for an incompressible fluid flow. For flow through a pipe of varying cross section, Bernoulli's equation shows that the pressure is the lowest at the smallest cross section where the velocity of the fluid is the highest. Bernoulli's equation is also applied to syphons.

  • Fluid Mechanic Magic
    Some non-intuitive demos show how ping pong balls behave in air streams.

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