Obviously, you would like to find out whether the hull has an intrinsic. So, this becomes an intrinsic characteristic of the hull, because intrinsically you have designed the hull. So, that if there is a disturbance, there it takes the straight line, know I give many examples for that, you take a pen or any any object, you through on the on the, you throw on an ear, what happens I will come back to this diagram.
I have this something object I throw on the ear. What is the trajectory text, you can throw and find out it may actually go like that. It does not follow a straight line right. See, if I just take a stick, I just some small some pencil and throw it in ear does it follow a perfect path like that. No, but now you put a mass here, and you put a feather here, like in an arrow. What happens, it goes exactly in a perfect line, and you understand that.
you see immediately you understand. Now, remember there is no rudder and all action here. You are just trying to find out intrinsic characteristic of this. So, this one has therefore, a directional straight line stability means it is following a straight trajectory. But this does not have, what does it tell, it tells us, obviously there is something happening. There is some characteristic, that defines or that kind of characterizes the straight line stability of an object.
Another example, you know that not a train. But in our younger days, there used to municipal cars which would have a small car (Refer Slide Time: 23:10), attached with the link number of small things. Now, you see you are going on a road remember it is not a train line. Now, you will always find that, when this goes they all follow like, you know this this this this are following. Why should it follow, remember the engine can be actually pulling it here this way. The the the motor and the last bogie is still like that, but it is still following this line.