Question

As more and more skyscrapers are built on the surface of Earth, does the day become longer or shorter? Explain your answer. (Note: In reality, this effect is so small it is not noticeable).

You are thrown a dropline from a helicopter and airlifted off the turntable. What happens to the angular velocity of the turntable? Explain why.

ans question in thoery not in diagrms please

Answer 1

1) As more and more skyscrapers are built, the moment of inertia of earth increases because the masses (building material) are now further apart from axis of rotation and since moment of inertia depends on distance, it increases. From conservation of angular momentum principle, the increase in moment of inertia leads to decrease in angular speed and hence the earth rotates slower and day's length would increase and it would become longer.

2) As you are lifted off, the moment of inertia of you+turntable decreases and from conservation of angular momentum principle, angular velocity of the turntable would increase.

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