Chapter 2 Flashcards
The word planet is derived from a Greek term meaning
Wanderer
The person who first showed that planetary orbits are ellipses was
Kepler
In an ellipse, the major axis is a distance measured
Along the longer diameter, passing through the foci of the ellipse
Where is a planet when it is moving mot rapidly in its orbit?
At perihelion
Mars moves in an elliptical orbit around he sun. The sun is located at
The focus of the ellipse that is closer to the point where Mars moves fastest
A major contribution of Johannes Kepler to the development of modern astronomy was
Proof that planetary obits are ellipses
Kepler’s 1st law states that a planet moves around the sun in a
Elliptical orbit, with the sun at one focus
A perfect circle is an ellipse wig an eccentricity of
Zero
Kepler’s 2nd law states hat a planet moves fastest when it
Is closets to the sun
Kepler’s 3rd law, the harmonic law, provides a relationship between a planet’s orbital
Period and the length of he semi major axis
1 AU is defined as
Mean distance between the earth and the sun
Why were Newton’s 3 laws so important to astronomy?
Newton’s laws showed that planets can move around the sub by hems elves forever, without coming to rest
According to newton’s 1st law
If no net force is acting on an object, hen both he object’s sped and direction of travel will be constant
Newton’s 2nd law states that
Force equals mass x acceleration
Acceding to Newton’s 3rd law, if a force is acting on an object, then
There must be some other force acting on a different object, with the same magnitude but in the opposite direction
