astronomy 2

• why does your weight vary across planets

  your weight is dependent on g , since w = mass x g , the gravitational field strength (g) of a planet varies depending on the size of the planet , this means your weight will also vary
• what is the gravitational field strength on earth

  approximately 10 N/kg
• what does our solar system consist of

  the sun (our star) , 8 planets (mercury , venus , earth , mars , jupiter , saturn , uranus , neptune)

  the planets natural satellites ( ie the moon)

  dwarf planets ,

  comets and asteroids
• what did ptolemy suggest about the universeand what was it known as

  that the earth was at th centre , the geocentric model
• what did copernicus suggest about the universe

  the sun is at the centre and planets orbit it
• what did galileo contribute to theories about the universe

  he used telescopes to support copernicus suggestions about the sun , and suggested the moon orbit planets
• describe the orbits of moons , planets , comets and artificial satellites

  they orbit in an eliptical shape
• explain why , for a stable orbit , the radius of orbit must change if speed changes

  at higher speeds , the object requires higher centripetal force , for a greater centripetal force , the gravitational force must increase , this is achieved by reducing the orbit radius
• explain how the force of gravity acting on a satellite affects its speed and velocity

  the force can alter its velocity since the direction is constantly changing , it cant affect its speed since there is no force component in the direction of motion
• what are disadvantages of telescopes located outside the earths atmosphere

  they are difficult to maintain as they have to be repaired in space ( or brought down , which is unreasonably expensive)
• what are the disadvantages if optical telescopes

  they can only be used at night when the sky is clear , they cant be used when the weather is cloudy
• evaluate the use of radio telescopes

  they are not weather dependent as radio waves are not blocked by clouds so they can be used in rain , they are usually large and expensive