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NEET
Exam
NEET
Subject
Physics
Chapter
Units and Dimensions

NEET · Physics · Units and Dimensions

The displacement y of a particle at position x and time t is given...

The displacement yy of a particle at position xx and time tt is given by the equation y=Acos⁡(Bt−Cx)y = A \cos(Bt - Cx). If Force (FF), Density (ρ\rho), and Time (TT) are chosen as the fundamental physical quantities, what are the dimensions of the quantity ABC\dfrac{AB}{C}?

Options

  1. A[F1/2ρ1/2T−1][F^{1/2} \rho^{1/2} T^{-1}]
  2. B[F1/2ρ−1/2T][F^{1/2} \rho^{-1/2} T]
  3. C[F1/2ρ−1/2T0][F^{1/2} \rho^{-1/2} T^0]
  4. D[F−1/2ρ1/2T0][F^{-1/2} \rho^{1/2} T^0]

Correct answer

C. [F1/2ρ−1/2T0][F^{1/2} \rho^{-1/2} T^0]

Step-by-step solution

According to the principle of dimensional homogeneity, the arguments of trigonometric functions must be dimensionless. Thus, the quantities BtandCxBt and Cx are dimensionless.

[B][T]=[M0L0T0]⇒[B]=[T−1][B][T] = [M^0 L^0 T^0] \Rightarrow [B] = [T^{-1}]

[C][L]=[M0L0T0]⇒[C]=[L−1][C][L] = [M^0 L^0 T^0] \Rightarrow [C] = [L^{-1}]

Since yy represents displacement, [A]=[L][A] = [L].

The dimensional formula for the required quantity is:
\left[\dfrac{AB}{C}\right] = \dfrac{[L][T^{-1}]}{[L^{-1}]} = [L^2 T^{-1}]<br><br>Let<br><br>Let[L^2 T^{-1}] = [F]^a [\rho]^b [T]^c<br><br>SubstitutingthestandarddimensionsforForce(<br><br>Substituting the standard dimensions for Force ([MLT^{-2}]),Density(), Density ([ML^{-3}]),andTime(), and Time ([T]):<br>):<br>[M^0 L^2 T^{-1}] = [MLT^{-2}]^a [ML^{-3}]^b [T]^c<br><br>[M^0 L^2 T^{-1}] = [M^{a+b} L^{a-3b} T^{-2a+c}]<br><br>Comparingthepowersof<br><br>Comparing the powers ofM,,L,and, andTonbothsides:<br>on both sides:<br>a + b = 0 \Rightarrow b = -a<br><br>a - 3b = 2<br><br>-2a + c = -1<br><br>Substituting<br><br>Substitutingb = -aintothesecondequation:<br>into the second equation:<br>a - 3(-a) = 2 \Rightarrow 4a = 2 \Rightarrow a = \dfrac{1}{2}<br>Thus,<br>Thus,b = -\dfrac{1}{2}.<br><br>Substituting.<br><br>Substitutinga = \dfrac{1}{2}intothethirdequation:<br>into the third equation:<br>-2\left(\dfrac{1}{2}\right) + c = -1 \Rightarrow -1 + c = -1 \Rightarrow c = 0<br><br>Therefore,thedimensionsof<br><br>Therefore, the dimensions of\dfrac{AB}{C}inthenewsystemarein the new system are[F^{1/2} \rho^{-1/2} T^0].<br><br>Answer:.<br><br>Answer:[F^{1/2} \rho^{-1/2} T^0]
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