Question

Assertion The measurement of $G$ by Cavendish's experiment, combined with the knowledge of $g$ and $R_E$ enables one to estimates $M_E$.
Reason By Newton's second law, the value of $g$ is given by the relation, $g=\frac{G{M}_E}{R_E^2}$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Assertion is incorrect but Reason is correct.

Answer 1

Answer: (A)

Henry-Cavendish experiment helped to determine the value of $G\left(G=6.67\times 10^{-11}N{m}^{2}k{g}^{-2}\right)$.
From the value of $g$ (acceleration due to gravity on the surface of the earth) and $R_E$ (radius of the earth)
using the relation $g=\frac{G{M}_E}{R_E^2}$ (by using Newton's law),
the mass of the earth $\left(M_E\right)$ can be estimated
$\Rightarrow M_E=\frac{g{R}_E^2}{G}$
where, $g=9.8m{s}^{-2}$,
$R_E=6400\times 10^{3}m$
and $G=6.67\times 10^{-11}N{m}^2/k{g}^2$.
Therefore, Assertion and Reason are correct and Reason is the correct explanation of Assertion.