Two small spheres of masses m and 4m attract each other with a force F0 when they are d metres apart.
(i) Express the force between the spheres when the separation is changed to 3d while the masses remain the same, leaving your answer in terms of F0.
(ii) Keeping the new separation 3d, the smaller mass is doubled while the larger mass is halved. Calculate the new force in terms of F0.