GATE | GATE CS Mock 2018 | Set 2 | Question 7

Three Gorges Dam crosses the Yangtze River in Hubei province, China. It is the world’s largest hydroelectric power station by total capacity of 22,500 MW. A shift in a mass of that size will impact the rotation of the Earth due to a phenomena known as “the moment of inertia”, which is the inertia of a rigid rotating body with respect to its rotation. The moment of inertia of an object about a given axis describes how difficult it is to change its angular motion about that axis. The longer the distance of a mass to its axis of rotation, the slower it will spin. Raising 39 trillion kilograms of water 175 meters above sea level will increase the Earth’s moment of inertia, and thus slow its rotation. However, the impact will be extremely small. NASA scientists calculated the shift of such a mass will increase the length of day by only 0.06 microseconds, and make the Earth only very slightly more round in the middle and more flat on the top. It will also shift the pole position by about two centimeters (0.8 inch).”
Choose the most relevant option based on above paragraph :

(A) This dam is a remarkable piece of engineering and increased the Earth’s moment of inertia very slightly.
(B) We can use ‘the moment of inertia’ to increase the length of day by making more such dams.
(C) Such projects should be made to slow the rotation of the earth.
(D) Such dams can make the shape of Earth flat, so should not be encouraged.

Answer: (A)

Explanation: By referring the above paragraph, only option (A) is relevant answer.

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