ramyani is correct

 

I the total force on the body at equator is mg'

GM/r^2=g acts towards the centre and w^2r acts away from centre(centrifugal accn with the frame of earth).

where g'=g-w^2r

hence centripital accn=w^2r=g-g'

hence if u know the effective gravitation u can find the centripital accn.

 

 

II if w^2r=9.8

w=(9.8/r)^1/2

 

the time taken for 1 complete rotation=2pie/w

 

=2pie(r/9.8)^1/2

 

=1.41hrs