SI unit of strain is

(A). Nm-2

(B). m

(C). N-m

(D). no unit

The SI unit of strain is actually (D) no unit. Strain is a dimensionless quantity that represents the deformation of a material when subjected to stress. To understand why it has no unit, let’s break it down further.

Understanding Strain

Strain is defined as the ratio of the change in length (deformation) of a material to its original length. Mathematically, it can be expressed as:

Strain (ε) = ΔL / L₀

• ΔL = Change in length
• L₀ = Original length

Why No Units?

Since strain is a ratio of two lengths, the units cancel each other out. For example, if you measure the change in length in meters and the original length in meters, the meters in the numerator and denominator cancel out, leaving you with a dimensionless quantity. This is why strain is expressed simply as a number, without any associated units.

Real-World Application

To illustrate this concept, consider a rubber band. If you stretch it from its original length of 10 cm to 15 cm, the change in length (ΔL) is 5 cm. The strain would be:

Strain = ΔL / L₀ = 5 cm / 10 cm = 0.5

This means the rubber band has been deformed by 50% of its original length, and you can see that the final value is simply a number, reinforcing that strain has no units.

Summary

In summary, the correct answer to your question is (D) no unit. Strain is a dimensionless measure of deformation, making it a unique and important concept in the study of materials and mechanics.