A body of mass 5 kg is raised vertically by 4 m at constant velocity (g = 10 m s⁻²). The work done against gravity is:
A100 J
B150 J
C200 J
D250 J
Answer & Solution
Correct answer: C. 200 J
1. Force needed to lift at constant velocity equals weight: F = m g = 5 × 10 = 50 N.
2. Displacement is 4 m, parallel to force.
3. W = F · d = 50 × 4 = 200 J.
_Source: NCERT Class 11 Physics Ch 5, §5.2 (worked-example methodology), p. 77_
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