IIT JEE , AIEEE Forum - Physics , Mechanics

sagar90

what is d value of g at centre of earth

srujana

$eq=0 !!$

$eq=g_d=g(1-\frac{d}{r})$

$eq=d=Depth$

When, $eq=d=r$

$eq=g_d=0$

Aatish

sagar90

but if we go by d formula
g=GM/R^2

sagar90

and if its 0 then why do an object is attracted towards d centre bcoz at infinite ht above the earth also g is zero.

anchitsaini

according to this formula M is the mass of earth attracting the body
=4/3 pie*r^3 *density
but r would be 0
hence g=0

anchitsaini

infinity is a hypothetical distance where earth's gravitational field cannot reach

sagar90

i didnt understood yaar

anchitsaini

which pt u are confused abt?

chetan_kp

gravitational force is due to the mass of the earth (in this case)
so at the centre of the earth the mass would be 0 so force acting on a body would be 0 so 'g' is 0
(but if u think in another complex way at the centre of the earth mass of the earth lies above him , but he is attracted in all the ditrections with the same magnitude , do 'g' is 0)

sagar90

think mathematically yaar g=GM/R^2
at centre R=0
there4 g will be infinity

anchitsaini

see u are confusing urself
Rcan't be 0 it is fixed to be radius of earth got it

g=GM/R^2
here the mass attracting the body would be 0 hence the answer

sagar90

yaaaaaa
i understood
but what about my 2nd question

anchitsaini

see first of all infinity is a hypothetical distance
still
who said that at infinity we think a body is attracted towards earth
we say that at infinity , earth's gravitational field is not there and hence a body is free from attraction

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