Question

Assuming that the mass $$m$$ of the largest stone that can be moved by a flowing river depends upon the velocity $$v$$ of the water, its density $$\rho $$ and the acceleration due to gravity $$g.$$ Then m is directly proportional to :

A. $${v^3}$$
B. $${v^4}$$
C. $${v^5}$$
D. $${v^6}$$  
Answer :   $${v^6}$$
Solution :
$$\eqalign{ & m \propto {v^x}{\rho ^y}{g^z} \cr & M \equiv {\left[ {L{T^{ - 1}}} \right]^x}{\left[ {M{L^{ - 3}}} \right]^y}{\left[ {L{T^{ - 2}}} \right]^z} \cr & {M^1}{L^0}{T^0} = {M^y}\,{L^{x - 3y + z}}\,{T^{ - x - 2z}} \cr & y = 1,x - 3y + z = 0, - x - 2z = 0 \cr} $$
Solving above equations
$$x - 3 - \frac{x}{2} = 0 \Rightarrow \frac{x}{2} = 3 \Rightarrow x = 6$$

Releted MCQ Question on
Basic Physics >> Unit and Measurement

Releted Question 1

The dimension of $$\left( {\frac{1}{2}} \right){\varepsilon _0}{E^2}$$  ($${\varepsilon _0}$$ : permittivity of free space, $$E$$ electric field)

A. $$ML{T^{ - 1}}$$
B. $$M{L^2}{T^{ - 2}}$$
C. $$M{L^{ - 1}}{T^{ - 2}}$$
D. $$M{L^2}{T^{ - 1}}$$
Releted Question 2

A quantity $$X$$ is given by $${\varepsilon _0}L\frac{{\Delta V}}{{\Delta t}}$$   where $${ \in _0}$$ is the permittivity of the free space, $$L$$ is a length, $$\Delta V$$ is a potential difference and $$\Delta t$$ is a time interval. The dimensional formula for $$X$$ is the same as that of-

A. resistance
B. charge
C. voltage
D. current
Releted Question 3

A cube has a side of length $$1.2 \times {10^{ - 2}}m$$  . Calculate its volume.

A. $$1.7 \times {10^{ - 6}}{m^3}$$
B. $$1.73 \times {10^{ - 6}}{m^3}$$
C. $$1.70 \times {10^{ - 6}}{m^3}$$
D. $$1.732 \times {10^{ - 6}}{m^3}$$
Releted Question 4

Pressure depends on distance as, $$P = \frac{\alpha }{\beta }exp\left( { - \frac{{\alpha z}}{{k\theta }}} \right),$$     where $$\alpha ,$$ $$\beta $$ are constants, $$z$$ is distance, $$k$$ is Boltzman’s constant and $$\theta $$ is temperature. The dimension of $$\beta $$ are-

A. $${M^0}{L^0}{T^0}$$
B. $${M^{ - 1}}{L^{ - 1}}{T^{ - 1}}$$
C. $${M^0}{L^2}{T^0}$$
D. $${M^{ - 1}}{L^1}{T^2}$$

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