28_gravitational

28_gravitational - Lesson 28: Mass, Weight, & Fields...

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Newton's work was all related to one goal he had for himself. .. to explain gravity. Newton realized that to explain the force due to gravity, he would first have to come up with a set of rules to explain forces in general. That's the stuff we've been working on in the last few lessons. Newton stated that a gravitational force exists between any two masses. According to his Third Law, this means that when you fall the Earth is pulling you down, while you are pulling the Earth with just as much force up. We don't see the Earth move because it has so much more mass than you that the Earth's inertia (tendency to keep doing what it is already doing) is enormous. Weight vs Mass Normally when a person wants to know his or her mass, they will just stand on a scale. Since this depends on the force due to gravity pulling you down, you are actually measuring your weight , a force acting on your body. Weight = F g = mg Your weight is measured in Newtons (just like any other force) and is different in different locations on Earth (since “g” varies from place to place). Mass is considered to a be constant anywhere in the universe. Floating in space, you could hold a car in your hand… it’s easy because it has no weight .
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This note was uploaded on 12/02/2011 for the course PHYSICS 235 taught by Professor Staff during the Fall '08 term at Rutgers.

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28_gravitational - Lesson 28: Mass, Weight, & Fields...

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