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Bashyboy
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Homework Statement
(a) Calculate the speed of a proton that is accelerated from rest through an electric potential difference of 121 V.
(b) Calculate the speed of an electron that is accelerated through the same potential difference.
Homework Equations
The Attempt at a Solution
I actually understand how to solve this particular problem, for the most part; when it comes to calculating the speed of the electron, there is one detail that confuses me: " The electron, since it has a negative charge, gains speed moving from Vi = 0 to Vf = 121 V. Why does the electron exclusively gain speed while moving in an electric field where Vi = 0 to a point in the field where Vf = 121? Why can't the proton also do this?
EDIT: For the proton, the conditions are: [itex]0 + qV_i = 1/2m_pv_p^2 + 0[/itex]
For the electron, the conditions are:[STRIKE] [STRIKE] [itex]0 + 0 = 1/2m_ev_e^2 + eV_f[/STRIKE][/itex] [/STRIKE]
Why do the equations differ so much? Why do they reverse the potential energy in each case?
EDIT: Conditions for the electron: [itex]0 + 0 = 1/2m_ev_e^2 - eV_f[/itex]
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