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Newton’s Law of Gravitation
Ms. Jeffrey-Physics
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GRAVITY Gravity is a force that exists between the Earth and the objects that are near it. The force of gravity causes an acceleration of all objects it interacts with. Acceleration of gravity ON EARTH = m/s2 (only if gravity is the only force acting on the object) This is the same value regardless of mass.
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Centripetal Force A force acting on an object that causes it to move in a circular motion. The Centripetal Force is directed towards the center of the circle in which it is orbiting Since the net force is directed towards the center of the circle, there is also an acceleration directed towards the center of the circle.
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Newton’s Findings The same force that causes objects on Earth to fall to the ground also causes objects in space to move along elliptical paths. Newton realized the acceleration due to gravity could cause the moon to orbit in an elliptical path around the Earth. The centripetal force acting on the moon, is the force of gravity supplied by the Earth.
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Universal Gravitation
Newton found that gravitation is universal: All objects attract each other with a force of gravitational attraction. Force of gravity between two objects is often negligible. The only force of gravity we actually feel is that of the Earth. Why is this?
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Factors That Affect Gravity
Mass What happens to the gravitational force on an object when mass is increased? Decreased? Distance Gravity becomes WEAKER with an increase in distance between two objects. Force of gravity is inversely related to distance! If we decrease the separation of two objects, what happens to the gravitational force between them?
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Force of Gravity vs. Distance
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Newton’s Universal Law of Gravitation
Force of gravity is directly proportional to the masses of the two objects and inversely proportional to the square of the distances between them. G is the Constant of Proportionality (found by Henry Cavendish) G = 6.67 x N m2/kg2
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Finding Force of Gravity on Earth
Use 6.38x106 m (the Earth’s radius) and 5.98x 1024 kg (mass of the Earth) to find the gravitational acceleration of the Earth.
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