AP Physics 1 Modified from original (and used with thanks) from author Gabe Kessler from OCHS

 A field force – a force that acts over a distance as opposed to only acting when in contact like friction or Normal force.

 Video Clip Video Clip

 any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

 Gravity - Family Guy Gravity - Family Guy

 The Sun has a mass of 2.0x10 30 kg and the Earth’s mass is 5.98x10 24 kg. The average distance between the center of Earth to the center of the Sun is 1.50x10 11 m. What is the force of gravity between the two? F g = G m m r2r2 F g = (6.67x ) (5.98x10 24 ) (2.0x10 30 ) (1.50x10 11 ) 2 F g = 3.5x10 22 N

 The force between the Earth and Sun is 3.5x10 22 N. What is the acceleration of the Earth to the Sun? a e = FgFg meme m / s 2 (3.5x10 22 N) (5.98x10 24 kg) =

 Notice the following:  To find the acceleration, simply use the above equation. What’s the acceleration on the surface of the Earth? a e = FgFg meme G m s m e m e * r 2 = G m s r2r2 = a = G m r2r2 (6.67x ) (5.98x10 24 ) (6.38x10 6 ) 2 = = 9.8 m / s 2

 Earth is pulling on a 3.5x10 5 kg asteroid with a force of 1.72x10 6 N. How far away is the asteroid from the center of Earth?  Solving the Universal Gravitation equation for r: r = (6.67x ) (5.98x10 24 ) (3.5x10 5 ) (1.72x10 6 ) r = 9.0x10 6 m G m a m e FgFg r = Pretty Darn Close!

 m 1 = 85 kg, m 2 = 55 kg, r = 1.5 m F g1 = G m 1 m 2 r2r2 (6.67x ) (85) (55) (1.5) 2 = F g1 = N

 Gravity is not only determined by how massive an object is but also the distance (or radius) between the center of masses  Earth may have a bigger mass, but it also has a bigger radius