IIT JEE , AIEEE Forum - Physics , Mechanics

cutie_divs91

The magnitude of the gravitational field at distances r1 and r2 from the centre of a uniform sphere of radius R and mass M are F1 and F2 respectively.then-

a) F1/F2=r1/r2 if r1<R and r2<R

b) F1/F12=(r1)2/(r2)2 if r1>R and r2>R

c) F1/F2=r1/r1 if r1>R and r2>R

d) F1/F2=(r1)2/(r2)2 if r1<R and r2<R

rooney

Its (A)

When radius is left, Gravitational field is given by F=Gm/rsquare
=Gx density x Volume enclosed /r square
Volume is directly proportional to r cube. So, F =K r. So, (a) is answer.

anandghegde

(A) and (B)

anandghegde

if r>R, the gravitational field due to a sphere F = GM/r²If r<R, the gravitational field due to a sphere F = GMr/R³

rooney

Yeah so if r>R, F1 would be inversely proportional to R1 square. So, answer cant be B.

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