### Earth?s Orbit

Initially believed to have a circular orbit, the Earth's orbit is actually elliptical. As the Earth orbits around the Sun in 365 days, its distance from the Sun varies between 147 and 152 million kilometers.

#### Amazing But True

- According to Newton's law, every object in the universe attracts every other object with a force that is directly proportional to the square of the distance that separates them:

if we rewrite the speed of the orbit in terms of its period we get,

- Learn more about the Earth's elliptical orbit: http://hyperphysics.phy-astr.gsu.edu/hbase/orbv.html

#### Show What You Know

Using the information provided above, answer the following questions.

- What force is keeping the Earth in orbit around the Sun?
- From the link provided, determine the reduced mass if
m1=4 kg andm2=6 kg . - If the Earth had a uniform density, how would you expect the force of gravity to change as you get closer and closer to the center of the earth?