Physics 3

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Physics 3
2012-12-06 14:56:40
nuclear fusion fission atom halflife bequerels

P2 revision
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  1. momentum is
    a measure of the state of movement of an object dependent on mass and velocity therefore momentum is a vector quantity
  2. momentum formula =
    momentum (kg m/s) = Mass (kg) X velocity (m/s)
  3. Force and momentum equation
    Force (N) = Change in momentum (kg m/s) / time taken for change(s)
  4. Crumple zones...
    increase the time taken for the bodys momentum to reach zero therefore reducing the force
  5. safety technology in cars includes
    crumples zones, cushioning during impact(air bags soft seating) and seat belts
  6. Work is done when
    a force moves on an object
  7. Work done (J) =
    Energy transferred (J)
  8. Work done (full formula) =
    Work done (J) = force (N) X distance moved in direction of force (m)
  9. Power =
    Work done (J)/time taken(s)
  10. Gravitational potential energy (J)=
    Mass (kg) X GFS (N/kg) X vertical height (m)
  11. Kinetic energy (j)=
    .5 X Mass(kg) X Velocity2 (m/s2)
  12. The principle of conservation of energy states
    energy cannot be created nor destroyed only transferred from one form into another
  13. What is an isotope?
    atoms of the same element that have a different number of neutrons
  14. the mass number of an atom =
    the number of protons+neutrons
  15. the atomic number of an atom =
    the number of protons
  16. an atom is unstable when
    its nucleus contains too many or too few neutrons
  17. when unstable nuclei split up they
    emit radiation
  18. what are the three main types of radioactive radiation?
    Alpha beta and gamma
  19. Alpha is
    most ionising least penetrating helium nuclei
  20. Gamma is
    Most penetrating least ionising high frequency electromagnetic wave
  21. beta is
    a fast moving electron quite ionising and quite penetrative 
  22. Nuclear fission is
    the process of splitting atomic nuclei
  23. Nuclear fission is a ___ ____
    chain reaction (self sustaining series of events)
  24. The products of nuclear fission are
    neutrons energy and daughter nuclei ( RADIOACTIVE)
  25. In a PWR control rods are used to
    control the rate of fission and therefore the power of the reactor
  26. In a PWR a moderator (water) is used to
    slow fast neutrons making them more likely to collide
  27. Nuclear fusion is
    the joining together of two or more light atomic nuclei
  28. Nuclear fusion is better because
    it produces more energy p/kg or fuel than fission
  29. we cannot use fusion because
    nuclei repel - have to be very close together (high pressure) Need to be moving very very fast to over come electrostatic repulsion and close enough to fuse together Temperature/pressure/confinement
  30. Background radiation is
    radiation that occurs all around us
  31. the activity of a radioactive isotope is
    the average number of disintegrations per second measured in becquerels and decreases over a period of time
  32. the half life of a radioactive isotope is a measurement of the rate of radioactive decay ie the time it takes for half the undecayed nuclei to decay
    got it?
  33. ionising radiation can
    damage cells and tissues causing cancer including leukaemia or mutations in the cells and can result in the bith of deformed babies in future generations
  34. The uses of radiation include
    radiotherapy, gammarays/x-rays, sterilisation of medical instruments, preserving foods, controlling sheet thickness,smoke detectors

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