A box with length $12\,\text{cm}$ and weight $0.43\,\text{N}$ rests on a horizontal table, with most of its length projecting beyond the table edge. The table edge serves as the pivot. The box's centre of gravity is located at its geometric centre. In order to keep the box balanced, a uniform sphere of diameter $2.4\,\text{cm}$ is placed inside the box so that it touches one end, as illustrated. Take the forces on the box to lie in the plane of the diagram. What is the minimum mass of the sphere required to keep the system in equilibrium?
- A$0.066\,\text{kg}$
- B$0.13\,\text{kg}$
- C$0.22\,\text{kg}$
- D$1.3\,\text{kg}$