 Welcome back mechanically, did you know that all major shape-changing operations make use of stress and strain to achieve the desired output? This makes us wonder, what are stresses and strain? Before we jump in, check out the previous part of this series to learn about what moment of inertia is. Now, stress is a physical quantity which expresses the internal forces that neighboring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material. For example, when a solid vertical bar is supporting a weight, each particle in the bar pushes on the particles immediately below it. The force between the bar and the particles is called stress, and the actual deformation of the particles is called strain. According to Hooke's law, when a material is loaded within its elastic limit, the stress induced in the material is directly proportional to the strain produced. It means the ratio of stress with the corresponding strain gives us a constant within its elastic limit. The constant is known as modulus of elasticity, or modulus rigidity, or more famously as the young's modulus. The stress induced in a body due to temperature changes is called thermal stress. The thermal stresses cause deformation doughty in the body, which is given by the product of alpha, which is thermal expansion coefficient, length of the body L, and the difference in temperature. Hence, we first saw what stress and strain are, then studied the Hooke's law, and finally saw what thermal stresses are. So, like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also, thanks a lot for those constructive comments. You helped the channel grow. So here are the top mechanical years of our last videos.