An electron falls from rest through a vertical distance h in a un… - Vidyadip

MCQ

An electron falls from rest through a vertical distance $h$ in a uniform and vertically upward directed electric field $E.$ The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance $h.$ The time of fall of the electron, in comparison to the time of fall of the proton is

✓
smaller
B
$5$ times greater
C
equal
D
$10$ times greater

✓

Answer

Correct option: A.

smaller

a
$h = \frac{1}{2}\frac{{eE}}{m}{t^2}$

$\therefore \,\,t = \sqrt {\frac{{2hm}}{{eE}}} $

$\therefore \,\,t \propto \sqrt m $ as $'e'$ is same for electron and proton.

$\because $ Electron has smaller mass so it will take smaller time.

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