Question:

If density of earth increases $4$ times and its radius becomes half of what it is, our weight will

Updated On: Aug 15, 2022
  • be 4 times its present value
  • be doubled
  • remain same
  • be halved
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The Correct Option is B

Solution and Explanation

Weight, $w = mg = m \frac{4}{3} \pi GR \rho$ Now that: $R'=R / 2$ and $\rho'=4 \rho$ $\therefore \frac{w'}{w}=\frac{R' \rho'}{R \rho}=\left(\frac{1}{2}\right) \times 4=2$ $w'=2 w$ Hence our weight will be doubled.
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Concepts Used:

Gravitation

In mechanics, the universal force of attraction acting between all matter is known as Gravity, also called gravitation, . It is the weakest known force in nature.

Newton’s Law of Gravitation

According to Newton’s law of gravitation, “Every particle in the universe attracts every other particle with a force whose magnitude is,

  • F ∝ (M1M2) . . . . (1)
  • (F ∝ 1/r2) . . . . (2)

On combining equations (1) and (2) we get,

F ∝ M1M2/r2

F = G × [M1M2]/r2 . . . . (7)

Or, f(r) = GM1M2/r2

The dimension formula of G is [M-1L3T-2].