orbital motion, natural & artificial satellites

• what force allows planets & satellites to maintain their circular orbits?

  gravity
• how does gravity create orbits?

  • planets & satellites are constantly changing direction, which means they are constantly accelerating
  • this means it is constantly changing velocity (not speed)
  • in order for them to accelerate, gravity is directed towards the centre of the circle
  • this would cause them to fall, but since theyre already moving, it just makes them change direction
  • they keep accelerating towards what its orbiting, but the instantaneous velocity keeps it travelling in a circle
• if the speed of a stable orbit changes, what must also change?

  radius