| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Show by calculation that the torque balance is valid (rotational analog of Newton´s second law for a rigid body).
Answer: Torque balance is valid