Question

An electron and Alpha-particle are released from rest from the same height above a fixed surface in a region of uniform electric field 'Eo' in vertically downward direction. Neglecting the gravity find which will hit the surface first ?

Answer 1

Neglecting Gravity :

Final Answer :Alpha particle

Steps and Understanding :
1)Electroststic Force on charged particles is given by
F = qE
where q -> charge on particle
E -> Electric Field acting on particle

2) Charge on electron =
-1 e
where e -> 1.6 * 10^(-19) C

Charge on Alpha particle->
= 2e

3)Since, E° is vertically downward.
So, Force on electron
will be upward
=> So, It will not fall on the ground.
It will go up.

4) On alpha particle, Force will act in downward direction since charge is positive.
So, it will fall on the ground.
It is only particle falling on the ground, so It will reach first.
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Let as assume Proton is present, then too Alpha particle will reach first on the ground as charge on alpha particle is twice of proton.

=> F proportional to charge
=> Force on Alpha particle will be more than Proton in downward direction.