Two electrons each are fixed at a distance $2d$. A third charge proton placed at the midpoint is displaced…

Two electrons each are fixed at a distance $2d$. A third charge proton placed at the midpoint is displaced slightly by a distance $x$ ($x \ll d$) perpendicular to the line joining the two fixed charges. Proton will execute simple harmonic motion having angular frequency: ($m$ = mass of charged particle)
  1. πε0md32q212
  2. 2πε0md3q212
  3. q22πε0md312
  4. 2q2πε0md312

Solution

From the given condition, we have

Fnet q=-2Fq/qcosθ

Fnet q=-2·14πε0·q2d2+x22·xd2+x2

=-q22πε0xd2+x23/2

For x<<d,

Fnet q=-q22πε0 d3x

  a=-q22πε0·md3x

Comparing with equation of SHM a=-ω2x

  ω=q22πε0md3

Asked in: JEE Main 2021 (24 Feb Shift 2)

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