A person of mass 60 kg stands on a weighing scale in an elevator accelerating upward at 2 m/s² (g=10). The reading is
A. 48 kg
B. 60 kg
C. 72 kg
D. 120 kg
Answer: Option C
Solution (By JKSSB Mock Tests)
Apparent weight = m(g+a) = 60×(10+2) = 720 N, which corresponds to 72 kg mass on scale (if scale calibrated in kg under g=10). Reading 72 kg. Downward acceleration would reduce.
Explanation:
First law of thermodynamics: Energy is conserved in an isolated system. It changes forms (kinetic to potential etc.) but total constant. Perpetual motion machine impossible.
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