Question

The frequency $$\left( f \right)$$ of a wire oscillating with a length $$\ell ,$$ in $$p$$ loops, under a tension $$T$$ is given by $$f = \frac{p}{{2\ell }}\sqrt {\frac{T}{\mu }} $$   where $$\mu = $$  linear density of the wire. If the error made in determining length, tension and linear density be $$1\% , - 2\% $$   and $$4\% ,$$ then find the percentage error in the calculated frequency.

A. $$ - 4\% $$  
B. $$ - 2\% $$
C. $$ - 1\% $$
D. $$ - 5\% $$
Answer :   $$ - 4\% $$
Solution :
Given, $$f = \frac{p}{{2\ell }}\sqrt {\frac{T}{\mu }} $$    Taking log of both sides
$$\log f = \log \left( {\frac{p}{2}} \right) - \log \ell + \frac{1}{2}\log T - \frac{1}{2}\log \mu $$
Differentiating partially on both sides,
$$\eqalign{ & \frac{{df}}{f} = 0 - \frac{{d\ell }}{\ell } + \frac{1}{2}\frac{{dT}}{T} - \frac{1}{2}\frac{{d\mu }}{\mu } \cr & {\text{or}}\,\,\frac{{df}}{f} \times 100 = \left( { - \frac{{d\ell }}{\ell } \times 100} \right) + \left( {\frac{1}{2}\frac{{dT}}{T} \times 100} \right) - \left( {\frac{1}{2}\frac{{d\mu }}{\mu } \times 100} \right) \cr & = \left( { - 1} \right) + \frac{1}{2}\left( { - 2} \right) - \frac{1}{2}\left( 4 \right) \cr & = - 1 - 1 - 2 \cr & = - 4\% \cr} $$

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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