Explanation:
In free fall under gravity alone, mechanical energy (kinetic + potential) is conserved, assuming no air resistance. Potential energy decreases while kinetic energy increases, sum constant. Law of conservation of mechanical energy. Non-conservative forces absent.
Explanation:
Tension is towards centre, displacement is tangential (velocity). Force perpendicular to displacement, cos90°=0, work zero. Centripetal force does no work, doesn't change speed.
Explanation:
Centripetal force acts radially inward, perpendicular to tangential displacement. Work W = F·d·cosθ; θ=90° ⇒ cos90°=0 ⇒ W=0. No energy transfer occurs; speed remains constant in uniform circular motion. Memory tip: 'Perpendicular force ⇒ zero work'. Conceptual question testing work-energy understanding, common in competitive exams to identify misconceptions about circular motion.
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