**Simple Stress**- is the intensity of force inside a solid material. The object is influenced that may lead to breakage or change on it's physical form.

It is force per unit area, which is basically Pascal (Pa) Newton per square meter or Megapascal (MPa) which is Newton per square millimeter.

The stress is spread out in the entire cross-section of the item that reacts to the external force or load applied.

**Different Kinds of Internal Forces:**

**Axial Force**- pull and or push action that is perpendicular to the cross section. Pull represents tensile force that tends to elongate the subjected member while Push represents compressive force that tends to shorten the subjected member, load usually denoted as P.**Shear Force**- total resistance to sliding the portion to one side of the exploratory section past the other in vertical or horizontal manner, usually denoted as Vx for horizontal shear force and Vy for vertical shear force.**Torque**- twisting the member either clockwise, counterclockwise or both, usually denoted as T.**Bending Moments**- resistance to bending the member about any axes, and are often denoted as M or Mx for moment about x-axis or My for moment about y-axis.

Studying material's strength is relevant to guarantee that the structure to be used will be safe against maximum internal forces that is produce by combining different kinds of loads.