Two uniform solid spheres made of the same material, with a constant density ρ\rhoρ, are placed in physical contact as shown in the diagram.
The smaller sphere has a radius R R\,R and the larger sphere has a radius 2R2R2R.
Which expression gives the magnitude of the gravitational force of attraction between the two spheres?
3281π2Gρ2R4\frac{32}{81}\pi^2 G \rho^2 R^48132π2Gρ2R4
6481π2Gρ2R4\frac{64}{81}\pi^2 G \rho^2 R^48164π2Gρ2R4
329π2Gρ2R4\frac{32}{9}\pi^2 G \rho^2 R^4932π2Gρ2R4
12881π2Gρ2R4\frac{128}{81}\pi^2 G \rho^2 R^481128π2Gρ2R4