Hi everyone, I have to answer some question about a physics lab..here are the questions A tank is empty by a pipe and we measure the height (y-y0) of fluid in the tank as a function of time. We obtain this graph ( I join the graph) We can find the relaxation time with the relation : with (yin -y0) is the initial height of the fluid in the tank and (y-y0) is the height of the fluid at a time t. I can easily isolate but the teacher say that it's a part of the graph which is the best to evaluate . He ask what is this part and why ?? It's a physic lab about the fluid flow and poiseuil equation for viscosity... If someone can give me some track .. Sorry for my English I'm French..