Why can a block of wood be regarded as a particle in force analysis, especially when it is on an inclined plane?

When the rotation of an object is not studied, it can be regarded as a particle.

After an object is regarded as a particle (usually selected at the center of gravity of the object), all the forces that the object receives in the force analysis act on the particle, which is convenient for the force analysis of the object.

Gravity, supporting force, friction, thrust, etc. When the wood block is on the inclined plane, it actually acts on different points or surfaces, which is not convenient for force analysis. These points of force have no influence on the actual force analysis of the object. Therefore, when a block of wood is on an inclined plane, it is usually abstracted as a particle.

For example, it is generally believed that gravity g acts on the center of gravity. This is just for the convenience of analysis. In fact, no matter where gravity is abstracted, it will not affect the results of stress analysis. The pressure of the wood block on the inclined plane is still m * g * cosa(a is the inclined plane angle), which has no effect.