 channel for physics. Please subscribe my channel. Hello everyone and welcome back to another episode of physics partner. Today we are going to discuss a very important physics law which is called Hooke's law. Hooke's law is also called law of elasticity. Before going to discuss the Hooke's law let us talk about a small history about Hooke's law. It was discovered by an English scientist named Robert Hooke in 1660. So let's do an experiment and understand Hooke's law. Before going for an experiment let us talk about some terms. The deforming force may be applied to a solid by stretching, compressing, squeezing, bending or twisting. There's a metal wire exhibits elastic behavior according to Hooke's law because the small increase in its length when is stretched by an applied force doubles each time the force is doubled. So according to Hooke's law the applied force F equals to the constant K times the displacement or change in the length. You can see on the screen the force is donated by the letter F and the unit is Newton and delta L is used for change in the length or the stretching length or the new length and K is the spring constant. Let us make it more easier. So what is the Hooke's law? According to Hooke's law if we apply the force on a spring the spring length will be stretched. The force and changing displacement or change in length is directly proportional to each other. Directly proportional means when you increase one physical quantity second physical quantity will also be increased. This is called directly proportional. Similarly when you decrease the first physical quantity second physical quantity is also be decreased. This is called directly proportional. Let's make it more easier by doing an experiment. So you can see here we have a small setup. We have iron stand, a spring and some masses and there is a measuring scale. If I add some mass so actually I am increasing the weight on the spring. So weight is considered as applied force. So look at one by one closely. When I increase the 10 gram mass it reach to 5 millimeters. Similarly I am increasing I am increasing like 20 gram which is 0.2 Newton and now it is 10. 30 which is 0.3 Newton and now it is 15. 40 is 0.4 and it is now 20. It means every time I am increasing the force the displacement is also be increasing. So this is the experimental verification of Hooke's law. So theoretically according to Hooke's law the applied force and the extension is directly proportional. You can say in other words also that stress and strain are directly proportional. Strength means the applied force and strain means the change in the length. If you look at the graph you can see it's a straight line graph which shows it is a directly proportional graph and you can see the spring constant value which is k 20 Newton per meter. But this law is applicable up to only a specific point. This specific point is called elastic limit. To understand elastic limit just consider a simple example of your daily life. If you stretch this spring multiple times the spring will come back to its original position. But if you stretch it with a very huge force the spring is deformed. It means you applied a force which crosses the elastic limit. The gradient of this line is showing the spring constant. So what if I add one more spring in series with the previous spring. So you can see there and if you add the weight you can see still follow the Hooke's law. But what is the difference? The difference is the value of the k. You can see the slope is now towards x axis. It means this angle is smaller now and the k value has become half of the last time. If you remember the last time the k value was 20 Newton per meter and now it is 10 Newton per meter. It means increasing the identical springs will make the Hooke's constant smaller. So what happen if I take two springs parallel to each other. Now you can try again to a placing weight. You can see it's still follow the Hooke's law. But this time the value of k is high. It is 40 Newton per meter and the slope is not towards x. Its slope is towards y. It means this angle is now smaller. It means the slope is now higher and the value of k is become double of it. It was 20 here. It is double here 40 whereas in that case it was half of it. So this is how we can explain the Hooke's law in a simple manner. Let me give some applications of Hooke's law in daily life. For example, spring balance. Trampoline enjoyed by the children. In the car there are springs similarly retractable pen. The Hooke's law is an important part of so many curriculums like IGCSE, Edexcel Pearson, Cambridge, AQA and other familiar curriculums. So this is a small video about the Hooke's law. According to Hooke's law the applied force is directly proportional to the change in the length of the stretch. Thank you very much for watching and listening. I hope you enjoyed the video. Take care of yourself. See you in the next video. Goodbye.