is a physical property of a material (metal, etc.) to stretch under the action of a load, force. The viscosity is determined by the force expended to break the adhesion of the molecules of a substance. Metals have different viscosities. To determine, tensile strength is used according to the following calculations: the initial length of the test rod (lo) and the final length after stretching (l) are measured. The ratio of the acquired length as a result of stretching to the original, expressed as a percentage, will be called the relative elongation.