orbital motion

• • planets, moons and artifical satellites orbit the Sun
  • planets orbit a star
  • moons orbit planets and are natural satellites
  • artifical satellites orbit the Earth and are man made
• • the solar system is apart of the Milky Way galaxy
  • this is a collection of billions of stars that are held together by gravity
• • planets orbit circularly around the Sun
  • circular orbits move at a constant speed, so its direction changes
  • a change in direction causes a change in velocity becuase velocity is a vector quantity
  • a chnage in velocity causes acceleration
• • the instantaneous velocity keeps the object orbiting circularly
  • this is caused by the gravitational force between the object and what it is orbiting
• • the closer to a star or planet, the stronger the gravitational force
  • the stronger force causes the speed to increase because the object needs to remain in orbit
  • for an object in a stable orbit, becaause the speed changes, the radius of the orbit will also change
  • faster objects will move with a stable orbit with a smaller radius
  • smaller objects will move with a stable orbit with a larger radius