Verified Answer :

F = G Mm/r²
mg = G Mm/r²
g = GM/r²
At centre of earth, r=0
g = GM/0
g =0

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\(\huge{\green{\tt{\underline{\underline{QUESTION:-}}}}}\)

Why value of 'g' is zero at center of Earth?

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\(\huge{\red{\tt{\underline{\underline{EXPLANATION:-}}}}}\)

When we move towards centre of earth, the mass is equally distributed in all directions.

The mass beneath you = Mass in front of you = Mass behind you

Thus, all the gravitational forces applied cancel each other and acceleration due to gravity (g) at centre of earth on centre of earth becomes zero (0).

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\(\huge{\green{\tt{\underline{\underline{PROOF:-}}}}}\)

The general equation of acceleration due to gravity is;-

g = \(\frac{GM}{r^2}\)

Assuming earth to be a perfect sphere and considering its uniform density.

We make the following adjustments in the following equation.

g = \(\frac{GM}{r^2}\)

Multiplying and dividing RHS by volume 'V'.

g = \(\frac{GM}{V} × V × \frac{1}{r^2}\)

We know that;-

\(\frac{M}{V}\) = Density, ρ

Therefore,

g = \(\frac{ρGV}{r^2}\)

For sphere;-

V = \(\frac{4}{3}\)π\(r^{3}\)

This makes

g = \(\frac{4}{3}\)π\(r^{3}\) × \(\frac{ρG}{r^2}\)

g = \(\frac{4πρG}{3}\)

So, at center of Earth

since, r = 0

so, g = 0.

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