What is the unit of strain and why is it unitless?

The unit of strain is unitless because it is a ratio of two lengths.

Strain is defined as the ratio of the change in length to the original length of an object. It is a measure of how much an object deforms under stress. Strain is expressed as a decimal or a percentage. For example, if a 10 cm long wire is stretched to 11 cm, the strain is 0.1 or 10%.

The unit of strain is unitless because it is a ratio of two lengths. The change in length and the original length have the same units, so they cancel out. This means that strain has no units. It is important to note that strain is not the same as stress, which is the force per unit area applied to an object. Stress has units of pressure, such as pascals or newtons per square metre.

Strain can be positive or negative, depending on whether the object is stretched or compressed. A positive strain means that the object has elongated, while a negative strain means that it has shortened. Strain is an important concept in engineering and materials science, as it helps to determine the strength and durability of materials under different conditions.