Answers

2016-02-05T23:08:50+05:30
Hi!
Total Height(h)=50 m
mass (m)=180000 kg
time = 1 hour = 3600 sec.
Potential energy (U) = m×g×h
⇒ U = 180000 × 10 × 50
⇒ U = 2×10⁸ J
half of the energy is converted into the electrical energy 
Final U = 2×10⁸/2 = 10⁸ Joules.
Power (P) = Work /time or energy/time
P = 10⁸/3600 = 10⁶/36 watt(W).
Power consumed by one lamp = P1 = 100 W
Number of the lamps lit(n) = P/P1
n=(10⁶/36)/100
n= 10⁴/36
 n= 277.77778
The number lamps lit will be 277.77778                               ans.
Only 277 lamps will be working properly and with proper functioning but the 228th lamp will not be lit perfectly as it is less power than the other lamps so it will glow dimly.
I hope answer is correct !
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