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NEET
Exam
NEET
Subject
Physics
Chapter
Units and Dimensions

NEET · Physics · Units and Dimensions

The force F acting on a particle is given by the equation F = (α -...

The force FF acting on a particle is given by the equation F=α−x2βtF = \dfrac{\alpha - x^2}{\beta t}, where xx is distance and tt is time. The dimensional formula of the ratio αβ\dfrac{\alpha}{\beta} is:

Options

  1. A[M−1L3T][\mathrm{M}^{-1} \mathrm{L}^3 \mathrm{T}]
  2. B[ML2T−2][\mathrm{M} \mathrm{L}^2 \mathrm{T}^{-2}]
  3. C[ML−1T−1][\mathrm{M} \mathrm{L}^{-1} \mathrm{T}^{-1}]
  4. D[MLT−1][\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]

Correct answer

D. [MLT−1][\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]

Step-by-step solution

According to the principle of dimensional homogeneity, quantities added or subtracted must have the same dimensions.

Therefore, the dimensions of α\alpha must be the same as those of x2x^2.
[α]=[x2]=[L2][\alpha] = [x^2] = [\mathrm{L}^2]

The dimensional formula for the entire equation is:
[F]=[α][β][t][F] = \dfrac{[\alpha]}{[\beta][t]}

Rearranging to find the dimensions of β\beta:
[β]=[α][F][t]=[L2][MLT−2][T][\beta] = \dfrac{[\alpha]}{[F][t]} = \dfrac{[\mathrm{L}^2]}{[\mathrm{M} \mathrm{L} \mathrm{T}^{-2}][\mathrm{T}]}
[β]=[L2][MLT−1]=[M−1LT][\beta] = \dfrac{[\mathrm{L}^2]}{[\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]} = [\mathrm{M}^{-1} \mathrm{L} \mathrm{T}]

Now, the dimensional formula of the ratio αβ\dfrac{\alpha}{\beta} is:
\left[\dfrac{\alpha}{\beta}\right] = \dfrac{[\mathrm{L}^2]}{[\mathrm{M}^{-1} \mathrm{L} \mathrm{T}]} = [\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]<br><br>Answer:<br><br>Answer:[\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]
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