 So, we are going to start fluid dynamics, fluid statics. So, you must know what is the amount for example or a break. So, in a must know how is the pressure variation in a static fluid, fine. So, in fact the buoyant force is nothing but a fine. So, our mass it will break, why we are focusing that problem must know how much load I can give to a fluid. So, we have hope the pressure will vary fine. So, that was our statics in the question. Now, we are moving forward is a fluid when it is flowing. What is the difference between flow and only. So, fluid statics will be applied there. So, when you shear force like this, resistance against this external force and that is what with the shear stress, ok. Whereas, the fluid offers no resistance to the shear force. Are you getting the difference? So, the shear stress is almost zero in the fluid. It can get deformed indefinitely. So, one layer of the fluid can move related to the other layer of the fluid. That is the difference between a solid and a liquid with respect to the flow. The shear deformation is called the flow itself. In fact, if you heat this solid, it will go towards the fluid behavior, fine. So, this is called the flow, alright. But, whenever we study the fluid property when water is flowing. So, just like in the fluid was flowing, we have to discuss the flow pipe will be drawn, a portion of pipe will be drawn and water is flowing inside, ok. Now, when I talk what do you think the kind of properties I am looking for? Ok, very smooth flow happens just because the flow is changed, right. So, when it has smooth flow and then, fine. So, our folk of the fluid flow when the flow is smoothly flowing, we will be going laminar or smooth flow what it does it mean and how we can find out. But, which flow it is? What else we will be finding out here? What do you think? Non-pistress, ok. What do you think? Someone said velocity, for example, when it comes and hits an AC generator's coil and then which turbine will generate the power and hydropower plants, fine. So, you should know what is the velocity, what kind of force water can exert on the turbine. That is just an example. What do you think the other problem is theorem is valid only for solids, only for gas or only for liquids. So, kind of energy and how do you write half energy square which mass it is, right. And similarly when we talk about and pipe is suppose what is such that it is inconvenient to apply in fluids. So, we need to modify that work energy theorem so that it becomes convenient for us to apply. Now, here is not there with solids. Why? Because entire solid remains as a single object, fine. So, you need not have single intact object, mass m is given to given. But, here the problem is the mass is continuously. So, I should not go against the conservation of mass. Somehow I have in fluid also it should not happen that is called continuity equation, fine. So, we are going to discuss these two theorems only continuity theorem and fluid dynamics is much more simpler than fluid statics even though the situation is little bit more important, much simpler. So, let us first discuss what is stream line flow. So, please write down stream line flow, we discussed that line suggest there has to be some sort of line. So, suppose you have this is nothing but fluid. Inside the big pipe lot of fluid particles might be there. Many fluid particles, infinite fluid particles are there. But the definition of stream line flow comes from the motion of a single particle. Let us say one such particle out of those infinite particle follows this path. It goes from 0.1 to 0.2 and it follows this path. The stream line flow is a flow for which the each particle if it enters point number 1 it will follow the 0.2 also. So, it is fixed. Are you getting it? That is what the stream line flow is. It somehow comes and touches this stream line it is going to follow this. So, in a stream line flow, it goes from 0.2 to 0.2 and it follows this path.