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JAMB Physics 1995 Question 9

Question 9

Gravitational Field

A body is projected from the earth's surface with the intention of letting it escape from the earth's gravitational field. What is the minimum escape velocity of the body? [Earth's radius = 6.4 × 103 km, g = 10 m s−2]

  1. A.14 km s−1
  2. B.13 km s−1
  3. C.12 km s−1
  4. D.11 km s−1
Show the answer and explanation

Answer: D (11 km s−1)

Explanation

Escape velocity v = √(2gR) = √(2 × 10 × 6.4 × 106) ≈ 1.13 × 104 m s−1, about 11 km s−1.