Question:

The value of g on earth's surface is $980\,cms^{-2}$. The value at a height of 64 km from surface of earth is

Updated On: Jul 7, 2022
  • $960.4\, cm s^{-2}$
  • $984.9 \,cm s^{-2}$
  • $982.45 \,cm s^{-2}$
  • $977.55\, cm s^{-2}$
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The Correct Option is A

Solution and Explanation

Using $g_h = g \frac{R^2}{(R + h)^2}$, we get $g_h = 980 \left(\frac{6400}{6400 + 64} \right)^2$ = 960 cm $s^{-2}$
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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].