Elasticity Class 9 Physics | Hooke’s Law Explained with Examples | FBISE/KPK BOARDS

Learn Elasticity and Hooke’s Law Class 9 Physics for FBISE and KPK Boards in this complete lecture. In this video, we explain the concept of elasticity, elastic limit, deforming force, restoring force, Hooke’s Law, spring constant, and practical examples. This lecture is very helpful for Class 9 Physics students preparing for board exams, tests, MCQs, short questions, and numerical problems. Topics Covered: What is Elasticity? Deformation of Solids Restoring Force Hooke’s Law Formula F = kx Elastic Limit Spring Constant Examples and Numerical Problems This lecture is specially designed for students of Federal Board of Intermediate and Secondary Education, KPK Board, and all Class 9 Physics learners. Elasticity and Hooke’s Law In our daily life, we often observe that when a force is applied to a body, its shape or size changes. If we stretch a rubber band, it becomes longer, and when we release it, the rubber band comes back to its original shape. This property of materials is called elasticity. Elasticity is defined as the property of a body due to which it regains its original shape and size when the deforming force is removed. However, not all materials show the same degree of elasticity. Steel, for example, is highly elastic because it returns to its original shape almost perfectly, whereas clay or putty has very little elasticity because once it is deformed, it does not return back to its original form. Thus, elasticity is one of the most important physical properties of solids. The extent of elasticity depends upon the material. Materials like rubber, steel, glass, and aluminum all have different elastic behaviors. In fact, steel is considered more elastic than rubber because it returns to its original length more perfectly when the force is removed, even though rubber stretches more. When we study elasticity, we also need to understand Hooke’s law, which is a fundamental principle in physics. Hooke’s law was discovered by Robert Hooke in the 17th century. According to Hooke’s law, the extension or compression produced in a body is directly proportional to the force applied, provided that the elastic limit of the body is not exceeded. Mathematically, Hooke’s law can be written as: F∝x or F=kx Here, F is the applied force, x is the extension or compression, k is the constant of proportionality, called the spring constant or force constant. The spring constant depends on the material and thickness of the spring or wire. A stiffer spring has a larger value of 𝑘 The concept of the elastic limit is very important when discussing Hooke’s law. The elastic limit is the maximum amount of stress or force per unit area that a material can bear while still being able to return to its original shape. If the force applied goes beyond this elastic limit, the material will not return to its original form and will be permanently deformed. For example, stretching a spring gently follows Hooke’s law, but if it is stretched too much, the spring may lose its shape. Elasticity and Hooke’s law are very important in practical life. Engineers and architects use these principles when designing buildings, bridges, and machines to make sure they can bear loads without permanent deformation. The working of springs, measuring instruments, and even vehicle shock absorbers are based on Hooke’s law. In conclusion, elasticity is the ability of a material to return to its original shape after deformation, and Hooke’s law gives us the mathematical relationship between force and deformation. Together, they form the basis of understanding how materials behave under forces, which is essential in science and engineering. Elasticity is the property of a material by which it regains its original shape and size when the deforming force is removed. For more amazing lectures please subscribe our channel. For more lectures of class 9th visit link below