To solve this question, we need to understand the concept of different types of stress that can act on a material. The question involves forces acting normally on the cross-section of a bar.

Types of Stress:

• Compressive Stress: This occurs when forces are applied in a manner that tends to compress or shorten the material.
• Tensile Stress: This occurs when forces are applied in a way that tends to elongate or stretch the material.
• Shear Stress: This occurs when forces are applied parallel or tangentially to the surface, causing one part of a material to slide past another.

Analysis of the Figure:

From the given figure, two forces are acting normally (perpendicular) on the cross-section of the bar. Both forces are directed towards each other, which means they tend to compress the bar.

Conclusion:

The forces are tending to shorten the length of the bar, which is the characteristic of compressive stress. Therefore, the type of stress introduced in the bar is compressive stress.

Justification of Answer:

• The forces act towards each other, compressing the material—characteristic of compressive stress.
• Tensile stress would require forces acting away from each other. This is not the case here.
• Shear stress involves parallel forces, which are not present here.

Therefore, the correct answer is: compressive stress.