Quick notes 5-5
1. People of Newton’s time period had difficulty understanding how gravity could
be a force because they were used to being able to see forces act upon objects, such
as a hand pushing a cart.
2. Newton determined the magnitude of the gravitational force exerted by Earth on
the moon compared to objects on the Earth’s surface and determined it was 1/3600,
which meant it was 1/3600g. Newton also determined that the moon is 60 times
further from the Earth’s center than objects on its surface. He also surmised since
60 squared is 3600 or the distance between the earth and moon squared (r2) was
inversely proportional to the gravitational force.
3. This led to the Law of Universal Gravitation:
Every particle in the universe attracts every other particle with a force that is
proportional to the product of their masses and inversely proportional to the square
of the distance between them. This force acts along the line joining the two
particles.
4. FG=G m1m2/r2
5. Henry Cavendish calculated G to equal 6.67 x 10 -11 Nm2/kg2