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Acceleration/ equation problem

  1. Sep 29, 2008 #1
    1. An electron of mass 9.11×10^−31 kg leaves one end of a TV picture tube with zero initial speed and travels in a straight line to the accelerating grid, which is a distance 1.20 cm away. It reaches the grid with a speed of 4.50×10^6 m/s. The accelerating force is constant.
    Find the acceleration.
    Find the time to reach the grid.
    Find the net force. (ignore gravity on the electron)




    2. v^2=(u^2)+2*a*s



    3. I plugged in the numbers to the equation v^2=(u^2)+2*a*s. to find acceleration, but the anwer (1.875*10^8) was incorrect. Is this the correct equation? The other answers should stem from the acceleration right?
     
  2. jcsd
  3. Sep 29, 2008 #2

    rl.bhat

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    (4.50×10^6 m/s.)^2 = 2*a*(1.2x10^-2)
    From the above equation find the value of a
     
  4. Sep 29, 2008 #3
    Acceleration - Sub into equation v2=u2+2aS -- make sure you only substitute after converting to SI units.

    Time - Use Equation a=(v-u)/t (Yes you need to find acceleration first)

    Net force - Use equation [tex]\sum[/tex]F=ma

    And 1.875*10^8 for acceleration is wrong.

    Hope this helps.
     
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