The random error in the arithmetic mean of $100$ observations is $x$; then random error in the arithmetic mean of $400$ observations would be

  • A

    $4x$

  • B

    $\frac{1}{4}x$

  • C

    $2x$

  • D

    $\frac{1}{2}x$

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In a simple pendulum experiment for determination of acceleration due to gravity $(g)$, time taken for $20$ oscillations is measured by using a watch of $1\, second$ least count. The mean value of time taken comes out to be $30\,s$. The length of pendulum is measured by using a meter scale of least count $1\, mm$ and the value obtained is $55.0\, cm$. The percentage error in the determination of $g$ is close to  ........... $\%$

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A student determined Young's Modulus of elasticity using the formula $Y=\frac{M g L^{3}}{4 b d^{3} \delta} .$ The value of $g$ is taken to be $9.8 \,{m} / {s}^{2}$, without any significant error, his observation are as following.

Physical Quantity Least count of the Equipment used for measurement Observed value
Mass $({M})$ $1\; {g}$ $2\; {kg}$
Length of bar $(L)$ $1\; {mm}$ $1 \;{m}$
Breadth of bar $(b)$ $0.1\; {mm}$ $4\; {cm}$
Thickness of bar $(d)$ $0.01\; {mm}$ $0.4 \;{cm}$
Depression $(\delta)$ $0.01\; {mm}$ $5 \;{mm}$

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Find the relative error in $Z,$ if $Z=\frac{A^{4} B^{1 / 3}}{ C D^{3 / 2}}$