# When a proton is released from rest in a room, it starts with an initial acceleration a0 towards west. When it is projected towards north with a speed 0 it moves with an initial acceleration 3a0 toward west. The electric and magnetic fields in the room are: Option 1) Option 2) Option 3) Option 4)

As we learned in @8252 and @8250

Acceleration of charged particle,

$\vec{a} = \frac{q}{m}\left ( \vec{E}+\vec{V}\times \vec{B} \right )$

Release from west $= \vec{a} = \frac{q}{w}\vec{E} = a_{o}\:\left ( west \right )$

$\Rightarrow \vec{E} = \frac{ma_{o}}{e}\:\left ( west \right )$

When it is projected towards north, acceleration due to magnetic force = 2ao

$\therefore$ Magnetic field, $B = \frac{2ma_{o}}{ev_{o}}\:\left ( down \right )$

Option 1)

This option is incorrect

Option 2)

This option is incorrect

Option 3)

This option is correct

Option 4)

This option is incorrect

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