A solid sphere of uniform density and radius R exerts a gravitational force of attraction F1 on a particle placed at P. The distance of P from the centre of the sphere is 2R. A spherical cavity of radius R/2 is now made in the sphere (that cavity passes thru centre of big sphere and also touches circumf of big sphere)g The sphere (with cavity) exerts a gravitational force F2 on the same particle at P. The ratio F1/F2= 7/9.
my doubt is thr r 2 ways of solving
1) finding c.m of remaiing mass ,then we get dist.=5R/2 AND ANS AS 25/14
2)using Force due to hollow sphere F2 = Force due to solid sphere ? Force due to removed mass then we get ans as 7/9.
why the first way is wrong??
