Moving with the sun

N M Hjelm1, C Hazlett, R Hsieh

  • 1Area of Excellence in Telemedicine, Faculty of Medicine, Chinese University of Hong Kong, and the Prince of Wales Hospital, NT, Shatin, Hong Kong. magnus_hjelm@hotmail.com

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Kepler's First Law of Planetary Motion

In the early 17th century, German astronomer and mathematician Johannes Kepler postulated three laws for the motion of planets in the solar system. He formulated his first two laws based on the observations of his forebears, Nikolaus Copernicus and Tycho Brahe.
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Simple Harmonic Motion and Uniform Circular Motion

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A square-threaded screw jack is a mechanical device widely used for lifting heavy loads or applying considerable force. Its operation is based on converting the force applied at its handle into a torsional moment, causing the upward impending motion of the screw. This movement is accomplished by overcoming the static friction between the threads of the screw and the jack.
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