Answer:
the light bulb can be illuminated 14700 sec (= 245 minutes or 4 hours and 5 minutes)
Step-by-step explanation:
the change in gravitational potential energy ΔE is
ΔE= m*g*h = ρ*V*g*h = 1000 kg/m³ * 1 m³ *9.8 m/s² * 100 m = 980000 J
where
ρ= density of water
V= volume of water
g= gravity
h= height
the energy required to illuminate a light bulb is
e*ΔE = P*t
where
P= power required by the lightbulb
t= time
e= efficiency
then
t = e*ΔE/P = 0.9 * 980000 J / 60 W = 14700 sec (= 245 minutes or 4 hours and 5 minutes)
