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Homework Help: Kinetic energy

  1. Oct 10, 2004 #1
    Q26. In the neck of the picture tube of a certain black-and-white television set, an electron gun contains two charged metallic plates 2.80 cm apart. An electric force accelerates each electron in the beam from rest to 9.60% of the speed of light over this distance. (a) Determine the kinetic energy of the electron as it leaves the electron gun. Electrons carry this energy to a phosphorescent material on the inner surface of the television screen, making it glow. For an electron passing between the plates in the electron gun, determine (b) the magnitude of the constant force acting on the electron, (c) the acceleration, and (d) the time of flight.
  2. jcsd
  3. Oct 10, 2004 #2
    i need help i dun know what to do
  4. Oct 10, 2004 #3
    im so lost on this supplementry problme and the text is of no help
  5. Oct 11, 2004 #4
    can anyone give me some hints how to solve this porblem, cuz im thinking the energy of the electron wud be 1/2mv^2
  6. Oct 11, 2004 #5
    :'( ....................im so lost
  7. Oct 11, 2004 #6
    You know the mass of the electron...

    Hence, you were right in thinking 1/2 mv2 is the energy of the electron and v = 0.96C where C is the speed of light...

    Now you know the final velocity and the initial velocity of the electron and the distance it travels... come in newton... equation of motion...

    V2 - U2 = 2*Acc*Distance

    Which will give you Acc...
    Force = Mass * Acc.... so there you go...

    Proceed along those lines and you should be good...
  8. Oct 11, 2004 #7
    its 9.60%=9.60/100=0.096c?? right im sure that was juss a typo??
  9. Oct 11, 2004 #8
    im gonna try it
  10. Oct 11, 2004 #9
    (a) 3.7*10^-16 Joules
    (b)F=1.34*10^.14 Newtons
    (c)a=1.48*10^16 m/s^2
    (d) time of flight=1.94*10^6 seconds
    please check my answers if u have time plz
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