Question

In a new system of units, the fundamental quantities mass, length and time are replaced by acceleration $$'a',$$ density $$'\rho '$$ and frequency $$'f'.$$ The dimensional formula for force in this system is

A. $$\left[ {\rho {a^4}f} \right]$$
B. $$\left[ {\rho {a^4}{f^{ - 6}}} \right]$$  
C. $$\left[ {{\rho ^{ - 1}}{a^{ - 4}}{f^6}} \right]$$
D. $$\left[ {{\rho ^{ - 1}}{a^{ - 4}}{f^{ - 1}}} \right]$$
Answer :   $$\left[ {\rho {a^4}{f^{ - 6}}} \right]$$
Solution :
$$F = ma = \rho \,{\text{volume}}\,'a'$$
To write volume in terms of $$'a'$$ and $$'f'$$
Volume $$ = {L^3} = {\left( {\frac{L}{{{T^2}}}} \right)^3}{T^6} = {a^3}{f^{ - 6}}$$
$$\therefore F = \rho {a^4}{f^{ - 6}}$$

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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