A horizontal electric field (E = (mg /q) exist in space, as shown in (Fig. 3.24.) A particle of mass m, having charge q, is attached at the end of a light insulated rod. If the particle is released from the position shown in the figure. Find the angular velocity of the rod when it passes through the bottom most position.
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Answer

B

Explanation

By work energy throrem `W_(g)+W_("elec")=DeltaKE`

`mgl(1-1/sqrt(2))+qExxl/sqrt(2)=1/2 mv^(2)-0`
`( :' E=(mg)/q) u=sqrt(2gl), W=u/l=sqrt((2g)/l)`