A cavity of radius R/2 is created in a sphere of radius R and mass M at the periphery and this mass is placed at a distance 2R from the centre of the sphere as shown in figure. The force between the two is
A 
B 
C 
D 
Ans 1:
Class : Class 7
I agree with Gh from Mahatma, Ghaziabad, options are not correctly provided in the question.
Ans 2:
Class : Class 10
I think it should be 7GM^2/256R^2
G is constant. M will become 7M/8 due to mass removal .M2 will be M/8 . Distance is 2 R . So the product is equivalent to the above. But I don't know how it is not in answers
Ans 3:
Class : Class 8
i think the above explanation is good and would be more accurate if shft of centre of mass is calculated