Question:

For a planet having mass equal to mass of the earth but radius is one fourth of radius of the earth. Then escape velocity for this planet will be

Updated On: Jul 20, 2024
  • $11.2 \,km/sec$
  • $22.4\, km/sec$
  • $5.6\, km/sec$
  • $44.8\, km/sec$
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The Correct Option is B

Solution and Explanation

$ v_e = \sqrt{2g R } = \sqrt{ \frac{2GM}{ R}}$
if R is 1/4th then $ v_e =2 v_{e - earth}$
$= 2 \times 11.2 = 22.4\, km/sec $
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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].