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Electron Projectile Motion

  1. Oct 14, 2010 #1
    1. The problem statement, all variables and given/known data

    In nanoscale electronics, electrons can be treated like billiard balls. The figure shows a simple device currently under study in which an electron elastically collides with a rigid wall (a ballistic electron transistor). The green bars represent electrodes that can apply a vertical force of 7.60·10-13 N to the electrons. If an electron initially has velocity components vx = 1.30·105 m/s and vy = 0 and the wall is at 45°, the deflection angle θD is 90°. How long does the vertical force from the electrodes need to be applied to obtain a deflection angle of 131°?

    2. Relevant equations

    Force*Delta.Time = Mass*Delta.Velocity

    3. The attempt at a solution

    I've spend a long time trying to figure this out. I'm trying to set Force*Delta.Time = Mass*Delta.Velocity.

    I know that the mass is 9.11 10^-31, the force is 7.60·10-13, and I need to find the velocity to solve for the time.

    I'm not sure how to find the velocity.

    Thanks for any help.
  2. jcsd
  3. Oct 16, 2010 #2


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    Homework Helper

    The vertical force on the electron is given. Mass of the electron is known. Find acceleration in the y direction.
    Vx is given. Find Vy by Vy = a*t.

    The velocity with which the electron hits tilting wall is given by

    V = sqrt(Vx^2 + Vy^2) making an angle θ such that tanθ = (Vy/Vx) with horizon.

    Angle made by the velocity to the inclined wall is (45 - θ).

    To make the deviation 131 degrees, the velocity must make an angle 65.5 degrees with the normal to the inclined wall.
    So 65.5 = 90 - ( 45 - θ)

    Solve for θ and find tanθ.

    From that you can find Vy and hence t.
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