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Chapter 12 Universal Gravitation. All objects in the Universe attract each other. True or False: The moon and planets are beyond the pull of Earth’s gravity. All objects in the Universe attract each other. True or False: The moon and planets are beyond the pull of Earth’s gravity. FALSE!!!.
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All objects in the Universe attract each other • True or False: The moon and planets are beyond the pull of Earth’s gravity.
All objects in the Universe attract each other • True or False: The moon and planets are beyond the pull of Earth’s gravity. FALSE!!!
Lets consider the moon and Newton’s first law • An object in motion will remain in motion in a straight line unless acted on by an outside force. • What is the outside force working on the moon?
Lets consider the moon and Newton’s first law • An object in motion will remain in motion in a straight line unless acted on by an outside force. • What is the outside force working on the moon? Gravitational Attraction
Force of Gravity (Fg ) • If two objects have masses, m1 and m2, with center of mass separated by distance, r, then, each object exerts an attractive force on the other. Formula for Universal Gravitation Fg = G m1m2 r2 G is the Universal Gravitation constant 6.67 x 10 -11 N·m2 kg2
Force of Gravity (Fg ) Fg = G m1m2 r2 With increasing altitude or distance, r, what happens to the Force of Gravity (Fg )?
Force of Gravity (Fg ) Fg = G m1m2 r2 With increasing altitude or distance, r, what happens to the Force of Gravity (Fg )? It Decreases!!!
Force of Gravity (Fg ) Fg = G m1m2 r2 How is Fg affected when: Mass 1 is doubled? When both mass 1 and mass 2 are doubled? When the masses are 2x as far apart? When they are 3 x as far apart?
Force of Gravity (Fg ) Fg = G m1m2 r2 How is Fg affected when: Mass 1 is doubled? Fgis doubled When both mass 1 and mass 2 are doubled? Fgis quadrupled (4x) When the masses are 2x as far apart? Fgis decreased by ¼ When they are 3 x as far apart? Fgis decreased by 1/9
Problem Solving: Calculate the force of gravity on a 3 kg mass at Earth’s surface. The mass of earth is 6 x 1024 kg and Earth’s radius is 6.4 x106 m. Fg = G m1m2 G= 6.67 x 10 -11 N·m2 r2 kg2
Problem Solving: Calculate the force of gravity on a 3 kg mass at Earth’s surface. The mass of earth is 6 x 1024 kg and Earth’s radius is 6.4 x106 m. Fg = G m1m2 G= 6.67 x 10 -11 N·m2 r2 kg2 F = (6.67 x 10 -11 N·m2/kg2)(3 kg) (6 x 1024 kg ) (6.4 x106 m)2 F = 29.31 N
Calculate the Force of Gravity on a 3 kg object 6.4 x 106 m above the Earth’s surface.
Calculate the Force of Gravity on a 3 kg object 6.4 x 106 m above the Earth’s surface. F = (6.67 x 10 -11 N·m2/kg2)(3 kg) (6 x 1024 kg ) (6.4 x106 m + 6.4 x106 m )2 F = 7.3 N
Law of Universal Gravitation PRACTICE