High school physics - force decomposition: when a force is decomposed, it is usually decomposed according to the actual effect of the force "When a force is decomposed, it is usually decomposed according to the actual effect of the force." How to understand this principle? Please explain thank you.

High school physics - force decomposition: when a force is decomposed, it is usually decomposed according to the actual effect of the force "When a force is decomposed, it is usually decomposed according to the actual effect of the force." How to understand this principle? Please explain thank you.

For example, the normal pressure only needs to consider the decomposition of the vertical force, and the horizontal force is ignored directly
For example, the sliding force on the inclined plane only needs to consider the horizontal and inclined plane forces, and the vertical inclined plane forces are directly ignored