Basic mechanics — name of stress produced when equal and opposite forces elongate a member When equal and opposite axial forces are applied to a prismatic bar causing it to elongate along its length, what is the stress called?

Introduction / Context:
Correctly identifying stress types is foundational in strength of materials and structural design. Members may be subjected to tension, compression, shear, bending, or torsion. Each stress state produces characteristic deformations and governs different design checks such as yielding, buckling, or rupture. Here the bar increases in length, a hallmark of axial tension producing tensile stress.

Given Data / Assumptions:

• Forces are equal, opposite, and collinear with the member’s axis.
• Cross-section and material are uniform; deformations are small.
• End constraints allow axial extension.

Concept / Approach:
Stress is internal force per unit area. Under axial pulls, normal stress acts over the cross-section with its line of action along the member’s axis. A positive axial strain (elongation) corresponds to tensile stress. The magnitude is sigma_tension = P / A for a uniform bar within elastic limits, where P is the axial force and A is the cross-sectional area.

Step-by-Step Solution:

Verification / Alternative check:
Hooke’s law in the elastic range gives epsilon = sigma / E; a positive strain (lengthening) means sigma is positive in tension. Visual checks in labs (extensometer readings) confirm elongation under tension.

Why Other Options Are Wrong:

• Compressive stress causes shortening, not elongation.
• Shear stress acts parallel to the area, leading to shear deformations, not pure axial elongation.
• Transverse stress is nonstandard terminology here; bending introduces normal stress that varies across the depth.
• Bearing stress is localized contact pressure, not uniform axial tension.

Common Pitfalls:
Confusing sign conventions; assuming any normal stress under axial load is compressive. Remember: pulling creates tensile stress; pushing creates compressive stress.

Final Answer:
Tensile stress