The escape velocity from the Earth's surface is approximately ($R = 6.4 \times 10^6$ m, $g = 9.8$ m/s²):
A$7.9$ km/s
B$11.2$ km/s
C$20$ km/s
D$1000$ m/s
Answer & Solution
Correct answer: B. $11.2$ km/s
Escape velocity from Earth's surface: $v_e = \sqrt{2gR}$ (using the surface relation $GM/R^2 = g$).
$v_e = \sqrt{2 \times 9.8 \times 6.4 \times 10^6} = \sqrt{1.25 \times 10^8} \approx 1.12 \times 10^4$ m/s $= 11.2$ km/s.
Option A ($7.9$ km/s) is the *orbital* velocity at Earth's surface, smaller by a factor of $\sqrt{2}$. That trap is identical to the one in the orbital-velocity question.
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