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    <title>MIT TechTV - Videos tagged with circle</title>
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      <title>Orbital Motion</title>
      <pubDate>2009-06-11 14:02:02 -0400</pubDate>
      <itunes:author>MIT Department of Physics Technical Services Group</itunes:author>
      <itunes:summary>An air puck is attached to a string that passes through the center of an air table. A weight is attached to the end of the string. The ball is set into rotation in a horizontal circle. When the weight is released, creating a constant force inwards, the radius of the path is shortened and the puck speeds up.

A similar effect is seen when the string wraps around a center rod like a tether ball.  This creates an increasing force, which causes the puck to inspiral more quickly.</itunes:summary>
      <itunes:duration>181</itunes:duration>
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