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QJEEM20Phde45: JEE Main 2020 Physics - Class 12 JEEM20Phde45 Solution: Two identical electric point dipoles have dipole moments and…

Two identical electric point dipoles have dipole moments p→1=pi^{\overrightarrow p _1} = p\widehat i and p→2=−pi^{\overrightarrow p _2} = - p\widehat i and are held on the x axis at distance ' aa ' from each other. When released, they move along the x-axis with the direction of their dipole moments remaining unchanged. If the mass of each dipole is 'm', their speed when they are infinitely far apart is :

Multiple Choice Options

  • A pa32π∈0ma{p \over a}\sqrt {{3 \over {2\pi { \in _0}ma}}}
  • B pa1π∈0ma{p \over a}\sqrt {{1 \over {\pi { \in _0}ma}}}
  • C pa12π∈0ma{p \over a}\sqrt {{1 \over {2\pi { \in _0}ma}}}
  • D pa2π∈0ma{p \over a}\sqrt {{2 \over {\pi { \in _0}ma}}}

Step-by-Step Verified Solution

JEE Main 2020 (Online) 6th September Evening Slot Physics - Electrostatics Question 144 English Explanation

Using energy conservation :

KEi + PEi = KEf + PEf

0 + 2KPa3×P{{2KP} \over {{a^3}}} \times P = 12mv2×2+0{1 \over 2}m{v^2} \times 2 + 0

⇒\Rightarrow v = 2P24πε0a3m\sqrt {{{2{P^2}} \over {4\pi {\varepsilon _0}{a^3}m}}}

= Pa12πε0am{P \over a}\sqrt {{1 \over {2\pi {\varepsilon _0}am}}}

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