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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
- 5 times greater
- equal
- 10 times greater
Correct answer: smaller
Solution
The time of fall depends on the acceleration, which is inversely proportional to the mass of the particle (a = qE/m). Since the electron has a much smaller mass than the proton, its acceleration will be much greater, leading to a smaller time of fall.
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