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Question:

An electron of mass M_e, initially at rest, moves through a certain distance in a uniform electric field in time t_1. A proton of mass M_p, also initially at rest, takes time t_2 to move through an equal distance in this uniform electric field. Neglecting the effect of gravity, the ratio t_2/t_1 is nearly equal to?

1836

1

MpMe

MeMp

Solution:

Correct option is B. MpMe
Electrostatic force, FE = eE (for both the particles)
But acceleration of electron, ae = FE/Me
and acceleration of proton ap = FE/Mp
S = 1/2 aet1² = 1/2 apt2²
∴ t2/t1 = √(ap/ae) = √(Me/Mp)