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1.Units, Dimensions and Measurement
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The measured value of the length of a simple pendulum is $20 \mathrm{~cm}$ with $2 \mathrm{~mm}$ accuracy. The time for $50$ oscillations was measured to be $40$ seconds with $1$ second resolution. From these measurements, the accuracy in the measurement of acceleration due to gravity is $\mathrm{N} \%$. The value of $\mathrm{N}$ is:
A
$4$
B
$8$
C
$6$
D
$5$
(JEE MAIN-2024)
Solution
$\mathrm{T}=2 \pi \sqrt{\frac{\ell}{\mathrm{g}}}$
$\mathrm{g}=\frac{4 \pi^2 \ell}{\mathrm{T}^2}$
$\frac{\Delta \mathrm{g}}{\mathrm{g}}=\frac{\Delta \ell}{\ell}+\frac{2 \Delta \mathrm{T}}{\mathrm{T}}$
$\quad=\frac{0.2}{20}+2\left(\frac{1}{40}\right)$
$=\frac{0.3}{20}$
$\text { Percentage change }=\frac{0.3}{20} \times 100=6 \%$
Standard 11
Physics
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