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Question: Answered & Verified by Expert
Consider a spongy block of mass $m$ floating on a flowing river. The maximum mass of the block is related to the speed of the river flow $v$, acceleration due to gravity $g$ and the density of the block $\rho$ such that $m_{\max }=k v^x g^y \rho^z(k$ is constant $)$. The values of $x, y$ and $z$ should then respectively be
(Mass of the spongy block is assumed to vary due to absorption of water by it)
PhysicsUnits and DimensionsTS EAMCETTS EAMCET 2019 (06 May Shift 1)
Options:
  • A $6,3,2$
  • B $6,-3,1$
  • C $3,6,1$
  • D $6,1,3$
Solution:
2540 Upvotes Verified Answer
The correct answer is: $6,-3,1$
Since, the maximum mass of the block
floating on river depends, speed of flow of the river $=v$, acceleration due to gravity $=g$ and density of the block $=\rho$,
$m_{\max }=k v^x g^y \rho^z$
Compairing the dimensions of $\mathrm{M}, \mathrm{L}$ and $\mathrm{T}$ on both
sides, we get
$z=1$
$\begin{aligned} x+y-3 z & =0 \\ -x-2 y & =0 \\ x+y-3 \times 1 & =0[\text { [From Eq. (i) and (ii)] } \\ x+y & =3\end{aligned}$
From Eqs. (iii) and (iv), we get
$-y=3 \Rightarrow y=-3$
From Eq. (iv), we have
$\begin{aligned} & & x-3 & =3 \\ \Rightarrow & & x & =6\end{aligned}$
Hence, the value of $x, y$ and $z$ will be $(6,-3,1)$.

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