Two $2\mathrm{.}5-$cmcm$-$diameter disks spaced $2\mathrm{.}0$ mmmm apart form a parallel$-$plate capacitor. The electric field between the disks is $5\mathrm{.}21055\mathrm{.}2105$ V$/$mV$/$m$.$

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Part A

What is the voltage across the capacitor?

Express your answer with the appropriate units. An electron is launched from the negative plate. It strikes the positive plate at a speed of $2\mathrm{.}11072\mathrm{.}1107$ m$/$sm$/$s$.$ What was the electron's speed as it left the negative plate?

Express your answer with the appropriate units.