Question:

Acceleration due to gravity at earth's surface is $g \,ms ^{-2}$. Find the effective value of gravity at a height of $32\, km$ from sea level $:\left(R_{e}=6400 \,km \right)$

Updated On: Jul 27, 2022
  • $0.5\,g\,ms^{-2}$
  • $0.99\,g\,ms^{-2}$
  • $1.01\,g\,ms^{-2}$
  • $0.90\,g\,ms^{-2}$
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The Correct Option is B

Solution and Explanation

For height $h$ above the earth's surface $g'=g\left(1-\frac{2 h}{R_{e}}\right)=g\left(1-\frac{64}{6400}\right) $ $\left(\because R_{e}=6400 \,km \right) $ $=g(1-0.01) $ $= 0.99\, g\, ms ^{-2}$
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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].