A proton sists at coordinates (x,y)=(0, 0), and an electron at (d, h), where `d gt gt h`. At time `t=0` a uniform electric field E of unknown magnitude but pointing in the positive y direction is turned on. Assuming that d is large enough that the proton electron interaction is negligible, the y coordinates of the two particles will be equal (at equal time)

Options

A. at about y `=h//2000`
B. at an undetermined value since E is unknown,
C. at about `y=h//43`,
D. nowhere: they move in opposite sirections

Answer

A

Explanation

`a_("electron")=(q_(e)E)/m_(e)` & `a_("proton")=(q_(p)E)/m_(p)`
`S_("electron")/S_("proton")=(1/2 a_(e)t^(2))/(1/2 a_(p)t^(2)) rArr m_(p)/m_(e)`
`S_(e)+S_(p)=h`