Question

Question 3 10 pts In a small dam, water flows at a rate of 2500 kg/s and falls 30 m. After calculating the power wasted by the waterfall, how many 75 W lightbulbs can be lit by this power? O 75000 bulbs 9800 bulbs 2940 bulbs 7350 bulbs

Answer 1

Power is rate of change of energy P= du/dt

Mass per unit second dm/dt = 2500kg/s

Water fall from height h = 30m.

So change in potential energy of water U = mgh

So rate of change of potential energy

du/dt = ghdm/dt

P = 9.8×30×2500

P= 735000N/s

Power used by one bulb is 75W

So power used by x bulbs is 75xW

Total power is 735000N/s

So 75x = 735000

X= 9800 bulbs