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6. system of particles and rotational motion — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics6. system of particles and rotational motion1 Mark
MCQ
Different minerals are being mined from within the earth and multi-storeyed complexes are being constructed. Due to this activity theoretically
  • A
    Angular speed of earth would increase
  • B
    Angular momentum would increase
  • C
    Time period of earth would decrease
  • ✓
    Length of day would increase
✓

Answer

Correct option: D.
Length of day would increase
d
(d)

Consider the problem,

In the case of mineral, coverage area (r) increases

Therefore, Inertia $I = Mr ^2$

If $r$ increases, then $I$ increases

and, also $L = I \omega$

$L$ is conserved, then if $I$ increases, $\omega$ decreases.

And also, $\omega=\frac{2 \pi}{T}$

If $\omega$ decreases, then Time period ( $T$ ) increases.

Therefore, length of the day increases.

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