Given:
Initial distance between the two planets is 3 AU
Final distance between the two planets is 1 AU
Required: Change in gravitational force.
Step-by-step explanation:
The relation between gravitational force and distance is
![F\propto(1)/(r^2)](https://img.qammunity.org/2023/formulas/mathematics/college/3hs1kmbt1j5cfoe6evom0av0z4ip1l9lko.png)
The initial gravitational force is
![F_i\propto\frac{1}{9\text{ AU}}](https://img.qammunity.org/2023/formulas/physics/college/izdhgvgv79tgpx8lrk10teohxcl8jg6625.png)
The final gravitational force is
![F_f\propto\frac{1}{1\text{ AU}}](https://img.qammunity.org/2023/formulas/physics/college/c5htxon1ctfv4mipgqj9wy6bnxrenn27hi.png)
As the force is inversely proportional to the distance squared.
Thus, the force is increased by 9x.
Final Answer: The gravitational force increased by 9x