Harvard Natural Sciences Lecture Demonstrations
  • Pendulum Waves

    10,458,891 views 7 years ago
    Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and (seemingly) random motion.

    For more details see http://sciencedemonstration......

    The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations.

    Our apparatus was built from a design published by Richard Berg [Am J Phys 59(2), 186-187 (1991)] at the University of Maryland. The particular apparatus shown here was built by our own Nils Sorensen.

    Video courtesy of Harvard Natural Sciences Lecture Demonstrations, © 2010 President and Fellows of Harvard College Show less
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    • Coanda Effect - Duration: 3 minutes, 49 seconds.

      • 11 months ago
      Fluids flowing near a surface tend to follow the shape of the surface. Using Schlieren optics, we can see this behavior. It is known as the Coanda Effect and its explanation depends on viscosity, ...
    • Ultrasonic Levitation - Duration: 4 minutes, 34 seconds.

      • 1 year ago
      Acoustic levitation meets Schlieren optics: By reflecting a sound wave back onto itself, one can secure a standing wave if the distance between the source of the sound and the reflector is equal to...
    • Fire Tornado - Duration: 2 minutes, 12 seconds.

      • 1 year ago
      A story of one man's love of a fire tornado demonstration. A small metal container sits in the center of a 13" diameter turntable. Bending and clamping a brass screen (10 wires per inch) around the...
    • Vacuum Cannon - Duration: 40 seconds.

      • 1 year ago
      High speed footage of a ping pong ball, propelled by air rushing into an evacuated tube, penetrating three empty soda cans. The PVC tube is 8 feet long and 1.5 inches in diameter, with a layer of m...
    • Sodium Absorption Lines - Duration: 85 seconds.

      • 1 year ago
      Burning of sodium bicarbonate in Bunsen flame produces sodium absorption lines in continuous spectrum. Sodium 'D' line absorption shows up as a black line in the yellow of a continuous spectrum. Go...
    • Reverse Sprinkler - Duration: 94 seconds.

      • 2 years ago
      Which direction does a lawn sprinkler spin if fluid enters the nozzle rather than being expelled from it? Inspired by Richard Feynman's story in his 1985 book "Surely You're Joking, Mr. Feynman."

    • Meissner Effect - Duration: 2 minutes, 46 seconds.

      • 2 years ago
      A permanent magnet begins to hover above a ceramic material as it cools and transitions to a superconducting state; the magnet remains aloft until the ceramic warms above a critical temperature.

    • Mousetrap Fission Setup - Duration: 52 seconds.

      • 3 years ago
      Woflgang and Allen quickly and efficiently prepare the Mousetrap Fission demo for Robert Kirshner's The Energetic Universe course on February 26, 2015. The demo consists of 110 mousetraps armed wit...
    • Thin Film Interference (part 2) - Duration: 2 minutes, 59 seconds.

      • 3 years ago
      Close up of a thin film of soapy water that is vertically suspended across a 19 cm diameter plastic ring and illuminated with white light. Gravity pulls down on the film to make it much thinner in ...
    • Thin Film Interference (part 1) - Duration: 4 minutes, 26 seconds.

      • 3 years ago
      Wide shot of a thin film of soapy water that is vertically suspended across a 19 cm diameter plastic ring and illuminated with white light. Gravity pulls down on the film to make it much thinner in...
    • Cloud Chamber - Duration: 3 minutes, 38 seconds.

      • 4 years ago
      The trajectories of individual charged particles leave behind cloudy trails as they ionize the cooled, supersaturated air-alcohol vapor inside this diffusion cloud chamber. Alpha particles from the...
    • Schlieren Optics - Duration: 2 minutes, 52 seconds.

      • 4 years ago
      Demonstration of an optical technique that allows us to see small changes in the index of refraction in air. A point source of light is reflected from a concave mirror and focused onto the edge of ...
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  • Newtonian Mechanics Play all

    Laws of Motion, Momentum, Rotational Dynamics
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  • Fluids Play all

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  • Oscillations and Waves Play all

    Simple Harmonic Motion, Resonance
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