At the time when external forces act on a body, then its internal effects decide the strength of the materials.
When machinery things are discussed, then it is taken as a rigid body. However, it is also true that the deformable bodies have internal force and the analysis of it explains the strength of that body. So, it is true that we consider some bodies as the rigid body, but in case of external forces, some deformation takes place. So, in the cases when you have the proper investigation, then it is said that no object is a perfect rigid body.
Now, go through the following figure and understand the case carefully.
Here, W load is lifted with the help of this crowbar and force P.
Value can be written as
The two conditions are very important to keep in mind after evaluating the force P –