Gravitational fields

Two uniform solid spheres made of the same material, with a constant density $ρ\rho$ , are placed in physical contact as shown in the diagram.

Two uniform solid spheres in contact

The smaller sphere has a radius $R\,$ and the larger sphere has a radius $2 R$ .

Which expression gives the magnitude of the gravitational force of attraction between the two spheres?

$3281π2Gρ2R4\frac{32}{81}\pi^2 G \rho^2 R^4$

$6481π2Gρ2R4\frac{64}{81}\pi^2 G \rho^2 R^4$

$329π2Gρ2R4\frac{32}{9}\pi^2 G \rho^2 R^4$

$12881π2Gρ2R4\frac{128}{81}\pi^2 G \rho^2 R^4$

Gravitational fields Questions

Two uniform solid spheres made of the same material, with a constant density $ρ\rho$ , are placed in physical contact as shown in the diagram.

Two uniform solid spheres in contact

The smaller sphere has a radius $R\,$ and the larger sphere has a radius $2 R$ .

Which expression gives the magnitude of the gravitational force of attraction between the two spheres?

$3281π2Gρ2R4\frac{32}{81}\pi^2 G \rho^2 R^4$

$6481π2Gρ2R4\frac{64}{81}\pi^2 G \rho^2 R^4$

$329π2Gρ2R4\frac{32}{9}\pi^2 G \rho^2 R^4$

$12881π2Gρ2R4\frac{128}{81}\pi^2 G \rho^2 R^4$