The extension of a material divided by its original length is known as what?

• A. Elasticity
• B. Strain
• C. Tension
• D. Deformation

Answer: (B)

The main idea here is strain, which measures how much something stretches relative to its original length. It’s calculated as the extension ΔL divided by the original length L0, giving ε = ΔL / L0. This ratio is dimensionless (or you can express it as a percentage). For example, if a 100 mm rod lengthens by 2 mm, the strain is 2/100 = 0.02, or 2%. This helps distinguish strain from other terms: elasticity is the material’s ability to recover its shape after loading, tension is the pulling force that causes the stretch, and deformation is the general change in shape or size. Strain specifically describes the proportional change in length, not the force or the change itself.