Question

The period of oscillation of a simple pendulum is $$T = 2\pi \sqrt {\frac{L}{g}} .$$   Measured value of $$L$$ is $$20.0 \,cm$$  known to $$1 \,mm$$   accuracy and time for $$100$$ oscillations of the pendulum is found to be $$90s$$  using a wrist watch of $$1s$$ resolution. The accuracy in the determination of $$g$$ is-

A. $$1\% $$
B. $$5\% $$
C. $$2\% $$
D. $$3\% $$  
Answer :   $$3\% $$
Solution :
$$\eqalign{ & {\text{As}},g = 4{p^2}\frac{l}{{{T^2}}} \cr & {\text{So}},\frac{{Dg}}{g}'100 = \frac{{Dl}}{l}'100 + 2\frac{{DT}}{T}'100 \cr & = \frac{{0.1}}{{20}}'100 + 2'\frac{1}{{90}}'100 \cr & = 2.72 \cr} $$
≃ 3%

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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