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bobred
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Homework Statement
An infinite metal plate occupies the xz-plane. The plate is kept at zero potential. Electrons are liberated from the plate at y = 0. The initial velocity of the electrons is negligible. A uniform magnetic field B is maintained parallel to the plate in the positive z-direction and a uniform electric field E is maintained perpendicular to the plate in the negative y-direction. The electric field is produced by a second infinite plate parallel to the first plate, maintained at a constant positive voltage [itex]V_{0}[/itex] with respect to the first plate. The separation of the plates is [itex]d[/itex]. Show that the electron will miss the plate at [itex]V_{0}[/itex] if
[itex]d>\sqrt{\frac{2mV_{0}}{eB^2}}[/itex]
Homework Equations
[itex]v_{x}=\frac{E}{B}\left(1-\cos\left(\frac{qB}{m}t\right)\right)[/itex]
[itex]v_{y}=\frac{E}{B}\sin\left(\frac{qB}{m}t\right)[/itex]
[itex]v_{z}=0[/itex]
The Attempt at a Solution
I know this produces a cycloid traveling in the minus x direction. If [itex]r[/itex] is the radius of a rolling circle then [itex]d>2r[/itex] to miss. I think I should be using conservation of energy but don't know the form of the velocity. I am assuming the perpendicular velocity will be the sum of a transverse and rotational velocity?