To determine where the point of application of the contact forces is located between a cube and an inclined flat surface at an angle of 45 degrees, let's analyze the situation step-by-step.
### Physical Setup:
1. Cube on Inclined Surface:
- The cube is placed on a flat surface inclined at 45 degrees to the horizontal.
- Gravity acts vertically downward.
2. Forces Acting on the Cube:
- Gravitational Force: Acts downward through the center of mass of the cube.
- Normal Force: Acts perpendicular to the inclined surface.
- Frictional Force: Acts parallel to the inclined surface (if there is friction).
### Analysis:
1. Point of Application:
- The point of contact forces between the cube and the flat inclined surface is influenced by the interaction between the cube and the surface.
- Considering stability and equilibrium, the most likely point of contact for the force is where the cube makes direct physical contact with the surface.
2. Lower Corner Contact:
- Given the surface inclination of 45 degrees, and that gravity pulls the cube downward, the lower corner of the cube in contact with the inclined surface would bear the contact forces.
- This corner point is the most natural and stable point considering both normal force and friction acting at that corner.
### Final Determination:
Given the physical scenario and the directions of the forces involved, the point of application of the contact forces would be expected at that lower corner.
Hence, the correct answer is:
At the lower corner of the cube that is in contact with the flat surface.
