my ship this is my axis what i am doing i want to find I y y how i can write I y y it is actually mass into you can say k y y square when k y y is radius of gyration about the y axis this the relevant radius gyration. Now, tell me from this from estimate these masses are more or less distributed going lower etcetera see suppose you take a cylinder uniformly distributed mass you can find out k y y you know that it will be somewhere here around here well it I do not recall, but we it will be something like something by root twelve etcetera what I mean is that if I these are difficult to estimate how do I estimate I have to we have go to weight curve I actually have to go to the weight weight distribution curve then take sectional weight then take square of that etcetera etcetera, but quite often getting weight curve of a shape is one of the most not difficult, but uncertain things because lot of weight come here and there all the time. So, for our purpose we can make a reasonably good estimate. What will be a good estimate a good estimate will be that if it is around l by 4 moment of inertia k y y around that not necessary may be may be around 25 percent to 30 percent you see what happen is lets lets take a logical guess if the mass was uniformly distributed like a cylinder moment of inertia is going to lie between somewhere here because you see masses which are further contribute more. So, if you see. In fact, m x square and integrate you will find here. So, if there is uniformly distribution of mass; that means, if mass was uniformly distributed it is something like 35 percent or. So, I think 33 35 percent of that. But in the ship case what happen you understand that masses are more in the central region sections are bigger as you go to h typically you have smaller section smaller mass on the other hand they contribute more. So, it’s very logical number one it can never be at 0.5 because 0.5 would mean as if all the mass is here it cannot be at a center. So, it appears from any practical point and it has been born out from large number of measurements it is around 25 percent 25 26 27 28 29 30 something like that.