ASTR 170B2 Lecture Notes - Lecture 7: Ellipse, Centripetal Force, Net Force
13 Sep 2018
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Astr ptys 170b2 - lecture 7 - force and energy. Kepler"s first law: each planet moves in an elliptical orbit. Kepler"s second law: imaginary line joining the sun and the planet sweeps out equal areas of an ellipse over equal intervals of time ( the planet moves faster when it"s closer to the sun) Kepler"s third law: semimajor cubed = period squared, more distant planets move more slowly (semi major axis is in au while period is in years) They obey them, as all objects in orbit around another do. 1st law : an object moves at a constant velocity if there is no net force acting upon it. Plain language: when an object is left alone, it maintains a constant velocity. Unit of force is a newton (n) Plain language: force depends on mass and acceleration. Change of motion changes constantly in a central force: a force.
