Assuming earth to be a sphere of uniform density, what is

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Assuming earth to be a sphere of uniform density, what is the value of ‘g’ in a mine 100 km below the earth’s surface? (Given, R = 6400 km)

1. 9.65 m / s²
2. 7.65 m / s²
3. 5.06 m / s²
4. 3.10 m / s²

Correct Option: A

We know that effective gravity g' at depth below earth surface is given by

g' = g		1 -	d
			R

Here, d = 100 km, R = 6400 km,

∴ g' = 9.8		1 -	100		= 9.65 m / s²
			6400