Question

when a electron Falls from rest through a vertical distance x in uniform and vertically up but director electric field direction of electric field reverse keeping magnitude same at Proton allowed to fall from rest ine it through the same height at the time of fall of electron in comparison to time of all of proton ​

Answer 1

Answer:

Explanation:

If I am right , this question is asked in NEET 2018 .

It's really easy equation . How , Let see ,

A rough daigram is shown in figure.

As you know, electron is charged particle , it experiences elctric force due to present in electric field E .

so, the force act on electron , F = eE

F = ma

eE = ma ⇒a = eE/m , here m is mass of electron.

because electron starts to move in rest , ∴ u = 0

Now, use S = ut + 1/2 at²

h = 0 + 1/2 (eE/m)t²

t = √{2hm/eE}

Similarly in case of proton,

t' = √{2hM/pE} , here M is mass of proton

You also know, magnitude of charge on proton equals electron.

so, e = p

∴ t' = √{2hM/eE}

Here it is clear that ,

t/t' = √{m/M}

But mass of proton >> mass of electron

∴ M >> m

∴ t/t' < 1

t < t'

Hence, time taken by electron is smaller than time taken by proton.

Method 2:- as you know, acceleration on electric field , a = qE/m

so, time taken to cover h distance = √{2hm/qE}

If h , E ,q are constant then, t  √m

Hence, Heavier charged particle take longer time.

So, electron take less time than proton.

Hope it helps.