PHYS 2101 Lecture : Lecture23
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Wednesday, march 14, 2012: hw9 due monday march 19 at 11:59pm, of ce hours mwf 12:30-1:30, exam 3 : tuesday march 20 @ 6pm in lockett 16 (our section, exam 3 covers chapters 10-12. Today : continue chapter 13, review problems from chapter 12. Vector addition: a uniform sphere of matter attracts an object on the outside as if all the sphere"s mass were concentrated at its center (note: this de nes the position) r2 = (re + h)2. Three 5 kg spheres are located in the xy-plane. The earth is not a point mass: this formula: 2 r 2 applies for point masses: theorem: the gravitational force due to a perfect sphere of matter is identical to that of a point particle located at the sphere"s com. Only if you are outside the sphere! Far from earth, g is smaller: ag = g. It orbits at an altitude of 600 km. ag = g me r 2.
