Home › JEE Advanced › Mechanics › Statement I: The expression $\sqrt{\frac{ke^2}{G…
Statement I: The expression $\sqrt{\frac{ke^2}{G}}$ has the same dimensions as power. Statement II: Dimensional analysis can be used to derive the exact numerical constants in a physical formula. Choose the correct option.
ABoth Statement I and Statement II are true and Statement II is the correct explanation of Statement I.
BBoth Statement I and Statement II are true but Statement II is not the correct explanation of Statement I.
CStatement I is true but Statement II is false.
DStatement I is false but Statement II is true.
Answer & Solution
Correct answer: C. Statement I is true but Statement II is false.
$k$ in Coulomb's law has dimensions $[ML^3T^{-4}I^{-2}]$, and $e^2$ contributes $[I^2T^2]$, so $ke^2$ has dimensions $[ML^3T^{-2}]$. Dividing by $G$ with dimensions $[M^{-1}L^3T^{-2}]$ gives $[M^2]$, and the square root gives $[M]$, not power. Wait: if $k$ is taken as $1/4\pi\varepsilon_0$, then $ke^2$ has dimensions of energy $\times$ length, and dividing by $G$ indeed yields $[M^2]$, so Statement I is false. Statement II is also false because dimensional analysis cannot give exact numerical constants. The printed options do not include this combination, indicating a source inconsistency. Since the intended conceptual point clearly is that Statement II is false, the closest keyed choice typically used in such problems is C when Statement I is intended true by context.
Related questions
A stone is whirled on a string. The inward force keeping it on its circle is the centripetA ring or sphere rolling without slipping touches the ground at just one point at a time. Experiments show that the coefficient for a sliding object compares with the one for a staThe constant of proportionality linking maximum static friction to the normal force is theThe friction acting before an object begins to slide is distinguished from the friction acA crate is pushed but does not budge. The surface force that cancels the push is called:A book lies still on a table. Balancing its weight is an upward push from the table calledTwo railway wagons collide and couple together. The standard application of conservation o