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NEET 2017 · Applications of Dimensional Analysis

Applications of Dimensional Analysis question from NEET 2017

Q65NEET 2017Medium

Applications of Dimensional Analysis

A physical quantity of the dimensions of length that can be formed out of c, G and e24πε0\frac{e^2}{4\pi\varepsilon_0} is [c is velocity of light, G is the universal constant of gravitation and e is charge]

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Answer: (d)

  1. e24πε0=Fr2\dfrac{e^2}{4\pi\varepsilon_0} = F r^2, so its dimension is ML3T−2ML^3T^{-2}.
  2. Ge24πε0G\dfrac{e^2}{4\pi\varepsilon_0}: M−1L3T−2⋅ML3T−2=L6T−4M^{-1}L^3T^{-2}\cdot ML^3T^{-2} = L^6T^{-4}; square root gives L3T−2L^3T^{-2}.
  3. Dividing by c2=L2T−2c^2 = L^2T^{-2} gives LL.
  4. So the answer is (d).
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