If equal and opposite forces applied to a body tend to elongate it, the stress so produced is called

The correct option is Tensile stress.

Let's understand the concept of stress and analyze the different options step-by-step:

1. Definition of Stress:
When external forces are applied to a body, it undergoes deformation. Internal restoring forces are created within the body to resist this deformation. Stress is defined as this internal restoring force per unit cross-sectional area of the body.
Mathematically, it is expressed as:

$\sigma =\frac{F}{A}$

where $\sigma$ is the stress, $F$ is the restoring force (equal in magnitude to the applied external force under equilibrium), and $A$ is the cross-sectional area.

2. Types of Stress:
Depending on the direction and nature of the applied forces, stress can be classified into different types:

• Tensile Stress: When two equal and opposite forces are applied along the longitudinal axis of a body to pull it outward, tending to stretch or elongate the body, the resulting internal resistance per unit area is called tensile stress.

• Compressive Stress: When equal and opposite forces are applied to push a body inward, tending to shorten or compress its length, the resulting internal resistance is called compressive stress.

• Tangential (Shear) Stress: When the forces are applied parallel or tangential to the surface of the body, causing one layer of the body to slide relative to another (deforming its shape), the resulting stress is called tangential or shear stress.

• Working Stress: This is the maximum allowable stress that a structural member or machine component is designed to withstand safely during actual operation, which is kept below the material's elastic limit.

Conclusion:
Because the forces applied to the body are equal, opposite, and tend to elongate it, the stress produced is specifically called Tensile stress.