Create a simplified model of a lake of water that is behind a dam and the water
ID: 1529287 • Letter: C
Question
Create a simplified model of a lake of water that is behind a dam and the water is being used to run a hydropower plant. In order to figure out the mass of water in the lake, we picture it has the shape of a rectangular box, 10 km long and 4 km wide. The lake has a uniform depth of 30 meters. Calculate the potential energy of the water in the lake. For the PE formula use the average height of all the mass of water in the lake, which would be 15 meters (half of 30 meters). 1 m3 (cubic meter) of water has a mass of 1,000 kg.
Explanation / Answer
Volume of water = (10 x 10^3 m ) x ( 4 x 10^3 m) x 30
= 1.2 x 10^9 m^3
mass of water = density x volume
= 1.2 x 10^12 kg
average height = h/ 2 = 15 m
Potential energy = m g h = (1.2 x 10^12 ) (15)(9.8)
= 1.764 x 10^14 J
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