Question:

The maximum vertical distance through which a full dressed astronaut can jump on the earth is $0.5\, m$. Estimate the maximum vertical distance through which he can jump on the moon, which has a mean density $\frac{2}{3}$ rd that of the earth and radius one quarter that of the earth.

Updated On: Jul 2, 2022
  • 1.5 m
  • 3 m
  • 6 m
  • 7.5 m
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The Correct Option is B

Solution and Explanation

On moon $g_{m} =\frac{4}{3} \pi g\left(\frac{R}{4}\right)\left(\frac{2 \rho}{3}\right)$ $=\frac{1}{6}\left(\frac{4}{3} \pi G R \rho\right)=\frac{1}{6} g$ Work done in jumping $=m \times g_{m} \times 0.5=m \times\left(\frac{g}{6}\right) m$ $h_{1} =0.5 \times 6=3.0\, m$
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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].