Final answer:
Basic assumptions for stress analysis under torsion include linearity, uniformity, and isotropy of the material. These assumptions simplify the analysis and allow the use of mathematical equations.
Step-by-step explanation:
When analyzing stress under torsion, we make certain basic assumptions. These assumptions include the material being linearly elastic, the material having uniform properties, and the material being isotropic. Linearly elastic means that the material's stress-strain relationship is linear, uniform properties means that the material's properties (such as its behavior under stress) do not vary across the object, and isotropic means that the material has the same properties in all directions. These assumptions help simplify the analysis of stress under torsion and allow us to use mathematical equations that describe the behavior of materials under this type of stress.