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NEET
Exam
NEET
Subject
Physics
Chapter
Units and Dimensions

NEET · Physics · Units and Dimensions

Match List I with List II. The force F acting on a particle in a...

Match List I with List II.

The force FF acting on a particle in a medium is given by the equation F=Ae−Bt+CD+x2F = A e^{-Bt} + \dfrac{C}{D + x^2}, where tt is time and xx is distance.

List IList II
(A) BB(I) [ML3 T−2][\mathrm{M} \mathrm{L}^3 \mathrm{~T}^{-2}]
(B) DD(II) [MLT−1][\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]
(C) AB\dfrac{A}{B}(III) [L2][\mathrm{L}^2]
(D) CC(IV) [T−1][\mathrm{T}^{-1}]

Choose the correct answer from the options given below:

Options

  1. A(A)-(III), (B)-(IV), (C)-(II), (D)-(I)
  2. B(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
  3. C(A)-(IV), (B)-(III), (C)-(I), (D)-(II)
  4. D(A)-(II), (B)-(I), (C)-(IV), (D)-(III)

Correct answer

B. (A)-(IV), (B)-(III), (C)-(II), (D)-(I)

Step-by-step solution

According to the principle of homogeneity of dimensions:

1. The argument of an exponential function must be dimensionless.
[Bt]=[M0L0T0]⇒[B]=1[T]=[T−1][Bt] = [\mathrm{M}^0 \mathrm{L}^0 \mathrm{T}^0] \Rightarrow [B] = \dfrac{1}{[\mathrm{T}]} = [\mathrm{T}^{-1}]
Thus, (A) matches with (IV).

2. Quantities added together must have the same dimensions. In the denominator (D+x2)(D + x^2):
[D]=[x2]=[L2][D] = [x^2] = [\mathrm{L}^2]
Thus, (B) matches with (III).

3. Every term in an equation must have the same dimensions as the whole. For the first term:
[Ae−Bt]=[F]⇒[A]=[MLT−2][A e^{-Bt}] = [F] \Rightarrow [A] = [\mathrm{M} \mathrm{L} \mathrm{T}^{-2}]
Then, \left[\dfrac{A}{B}\right] = \dfrac{[\mathrm{M} \mathrm{L} \mathrm{T}^{-2}]}{[\mathrm{T}^{-1}]} = [\mathrm{M} \mathrm{L} \mathrm{T}^{-1}]<br>Thus,(C)matcheswith(II).<br><br>4.Forthesecondterm:<br>[CD+x2]=[F]⇒[C][L2]=[MLT−2]<br>Thus, (C) matches with (II).<br><br>4. For the second term:<br>\left[\dfrac{C}{D + x^2}\right] = [F] \Rightarrow \dfrac{[C]}{[\mathrm{L}^2]} = [\mathrm{M} \mathrm{L} \mathrm{T}^{-2}]
[C]=[MLT−2]×[L2]=[ML3 T−2][C] = [\mathrm{M} \mathrm{L} \mathrm{T}^{-2}] \times [\mathrm{L}^2] = [\mathrm{M} \mathrm{L}^3 \mathrm{~T}^{-2}]
Thus, (D) matches with (I).

The correct matching is (A)-(IV), (B)-(III), (C)-(II), (D)-(I).

Answer: (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
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