1. what is weight force?
    the force on an object due to its position in a gravitational field
  2. what is work?
    the change in energy that occurs when a force is moving an object
  3. What is Gravitational Potential energy? (GPE)
    the work done to move an object from infinity to a point within the gravitational field
  4. what is a tajectory and what are it's components?
    the path a projectile takes as it is moving through the air

    • verticle component is acceleration due to gravity
    • Horizontal component is constant velocity
  5. What is escape velocity?
    the initial velocity required by a projectile to rise vertically and just escape the gravitational field of a planet
  6. what is g-force?
    the measure of acceleration on an object using acceleration due to gravity as a base unit
  7. where on the earth and in which direction should a rocket be fired for maximum velocity?
    on the equator and to the east
  8. key features of a low earth orbit
    • 200-1000km above earth
    • fast velocity
    • used for mapping
  9. Key features of geostationary orbit
    • 36000km
    • period of 24 hours
    • used for em communications
  10. what causes orbital decay?
    collision with air particles causing heat
  11. what are three issues associated with re-entry of a craft?
    • angle 5-7degrees
    • nose angled upwards
    • heat ionises surrounding air blocking communications
  12. what are the contributions of goddard?
    • helped pioneer first liquid fuel rockets
    • proved space travel was possible by proving thrust in a vacuum
    • solved many technical problems
  13. what are the five proprties of the aether?
    • fills all space
    • transparent
    • permeates all matter
    • extremely low density
    • high elasticity
  14. outline the principle of relativity
    • all motion is relative
    • cant detect v unless you have another frame of reference to compare it to
  15. what are the two main ideas of einsteins theory of special relativity?
    • The laws of physics are true in all inertial frames of reference
    • c is constnat
  16. explain the relativity of simultaneity
    events that are simultaneous in one frame of reference when approching c are not for another frame of reference
  17. explain mass dilation
    the mass of an object increases as its speed increases as mass and energy are interconvertible. at speeds approaching C mass increase is exponential
  18. explain length contraction
    the length of an object is affected by its speed relative to others. if a spaceship at C zooms past observed from earth it would seem shorter and earth will seem smaller from the ship
  19. explain time dilation
    time measured by observers that are in relative motion to eachother are different. man in a ship approachin C will see an earth clock moving slower and vice versa
  20. what experiment proved einsteins theories?
    the atomic clocks
  21. what are the standards for one second and one metre considering light is the only constant?
    • 1m = the distance light travells in a fraction of a second
    • 1s = the time it takes for a specific number of oscillations of the caesium 133 atom
  22. what are two problems with travelling at speed of light?
    • at current speeds it would take millions of years
    • infinate mass thus infinate acceleration
    • amount of fuel alone is prohibitive
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