Practice question
Question
A body is launched from Earth at 13.5km/s. What is its speed at infinity? (Escape speed = 11.2km/s)
Explanation
vf2 = vi2−ve2. vf2 = (13.5)2−(11.2)2 = 182.25−125.44 = 56.81. vf = 56.81≈7.54km/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 7.5 km/s. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
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