Orbital Motion

• Centripetal Force - the resultant force that is necessary to keep and object moving in a curved path

  • acts towards the centre of a circle
• • When an object moves in a circle at a constant speed, it is constantly changing velocity
  • A change in direction causes a change in velocity
  • A change in velocity results in acceleration
  • So an object moving in a circular path is accelerating even though its speed may be constant
  • An object will only accelerate if a resultant force acts on it
  • For an object moving in a circle, the resultant force is the centripetal force that acts towards the centre of the circle
  • Gravitational attraction provides the centripetal force needed to keep things in orbit
• Planets that are further away from the star they are orbiting take longer to complete one resolution due a larger orbital radius

  • as you get further away, gravity gets weaker
• Solar System - our sun and planets
• Star - a large ball of gas
• Moon - orbits a planet
• Planets - orbits a start
• Acceleration - the rate of change of velocity
• Satellite - objects orbiting planets or stars
• Orbit - a full resolution around something
• Ellipse - non-circular orbit
• Geostationary Orbit:

  • high altitude but at a low speed
  • orbital path is parallel to the equator
  • fixed position relative to the Earth's surface
  • e.g - communication satellites
• Polar Orbit:

  • low altitude but at a high speed
  • orbital path over Earth's poles
  • changing position relative to Earth's surface
  • e.g - monitoring satellites to cover different regions