In this physics video lecture for iit jee, we are going to discuss fluid mechanics. The topics we are going to discuss in this video are, what is a fluid, difference between density and relative density, pressure in a fluid, variation of pressure with depth, and a few example problems in physics.

So what is a fluid? **Fluid** is nothing but a substance which can flow, i.e. **fluids** and gasses. There is an example related to glass in the above video. The next topic discussed is density and relative density. Density is nothing but the mass of the object by volume of the object or ϱ =Mass/Volume. Moving on to relative density, it is the density of the substance at any temperature by the density of water at 4⁰C. It can also be written as R.D= (Density of the object)/(Density of water at 4℃). Further, we have discussed** pressure in a fluid**. And then derived the value of atmospheric pressure which is 1.013 X 105. Next, we discussed gauge pressure, which is absolute pressure – atmospheric pressure. Further, the last topic discussed is the variation of pressure with depth. Further, we have explained the derivation of variation of pressure with depth which is P1 = P0 + ϱgh. After the derivation, we could conclude that the pressure does not depend on the shape of the container and is only dependent on the height and the pressure due to the liquid column at a height h is ϱgh.

In the end, the exemplary problem will help you to understand the entire topic. **Fluid mechanics** is a pretty hard topic for iitee physics lectures, and if not studied and understood properly can lead to a lot of problems while solving the problems. So in order to avoid these problems, my dear future IITians make sure you understand this topic from its roots as it is an important topic for your IIT JEE exams.