Question

Water falling from a 50 m high fall is to be used for generating electric enegy. If `1.8xx10^5kg` of water falls per hour and half the gravitational potential energyh can be converted into electric energy, how many 100 W lamps can be it?

Answer 1

Correct Answer - A::B
`h=50m, m=1.8x10^5kg`
`P=100 watt`
P.E=mgh`
`=1.8xx10^5xx9.8xx50`
`=882xx10^5J`
Because half the potetnial energy is converted into electricital energy.
Electircal energy `=1/2P.E. =441xx10^5J/hr`
So, power in watt(J/sec)`=(441xx10^5)`
`:.` Number of 100 W lamps, that can be lit `
(441xx10^5)/(3600xx100)=122.5~~122`