PHYS 0834 Lecture 4: Gravity and Orbits
13 Feb 2017
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Inertia: an object in motion wants to stay in motion unless its acted on by an unbalanced force. A=f/m - mass resists change in motion. For every force there is an equal and opposite force. Gravity is an attractions between objects of mass. Moon orbits earth because it has less mass, more change in direction. An object falling towards another due to gravity. Less massive object is a satellite of the more massive object. The two objects orbit a common center of mass. Free fall: ship is falling towards the earth + so are the astronauts. Uniform circular motion: moving on a circular path at a constant speed. Gravitational force changes both the direction and the speed of the planet as it moves in its orbit. Results in kepler"s 2nd law of equal areas. Objects with higher orbital speeds can escape bound orbits to be in unbound orbits.
