The internal resistance developed to counteract an external force is known as what?

The internal resistance developed to counteract an external force is referred to as stress. Stress is a measure of the internal force per unit area within materials that arises from externally applied forces, uneven heating, or permanent deformation, and it plays a critical role in how materials respond to loads. When an external force is applied to an object, it creates an internal counterforce within the object that resists this external force, and this is quantified as stress.

In engineering contexts, understanding stress is crucial for analyzing material behavior under various loading conditions, designing structures, ensuring safety, and preventing failure. Stress is typically measured in units such as pascals (Pa) or psi (pounds per square inch), and it helps engineers determine whether a material can withstand the loads it will encounter in service.

Other options like strain, ultimate strength, and load have specific meanings in material science and engineering but do not accurately describe the internal resistance itself. Strain refers to the deformation resulting from stress, ultimate strength pertains to the maximum stress a material can withstand before failure, and load refers to the external forces applied to a structure or material. Understanding the distinction between these concepts is essential for effectively applying them in engineering practices.