 This is what we have seen, now let us see what happens in the rapid change in temperature. So now you will not allow it to equalize, you are going to bring it suddenly. Question is, when can you have a situation when rapid changes in temperature can occur? And do not give time. So you have your airship in a nice air conditioned hanger and take out suddenly. It will take some time for it to stabilize, during that time what will happen that is what we will see now. Similarly, you are flying the airship and suddenly it starts raining, suddenly you encounter very cold conditions. So during the time when the whole envelope cools down to the ambient condition it will take during that time this will be applicable. Similarly, if you are flying on a cold weather, so in the long distance or long endurance flight, the airship can encounter situations where there is a sudden change in temperature without giving the time for the equilibrium to take place. During these cases there will be a change in the gross and light lift, let us see. So you can look at this problem from 2 angles, one angle will be there is a change in the gross lift. So let us recall that delta Lg or the change in the gross lift is P s times 1 by T A2 minus 1 by T A1 times Kv, this we have seen last time. So the net lift difference I am repeating again is the gross lift difference and the balloon air difference. I am showing it is same thing as delta Lg and delta Wba. Now delta Wba is equal to 0 in this case because there is no time available for the system to respond and the balloon air to go out. If you give time then of course system will go into equilibrium but right now W, so therefore the net lift change will be equal to the gross lift change. So the net lift, so there will be a change in the lift. This is like you are not allowing the system to respond and suddenly temperature has changed. So therefore net lift will change. It will become 1 upon T A2 minus 1 upon T A1. Now what will happen? Will it reduce or increase if you go to a cold place? If T A2 is less than T A1, what is it? Increase. If you go to a cold place it will increase. Why? If T A2 is less than T A1, one more way of looking at the whole thing is that subjecting an airship to sudden change in the ambient temperature is like giving it a sudden super heat or super cooling depending on whether you are going into a hot place or a cool place. So from that angle look the expression is there will be a T A switch when component there. So now what we will do is we will assume that T A is constant but that is super heat applied. Now initially the airship is at T A1 and suddenly it goes at T A2. Therefore the delta T SH1 will be 0 to start with and that will be suddenly T A1 minus T A2. You can consider it as 0 super heat when you are flying and suddenly you are exposed to a super heat of T A1 minus T A2 because temperature has become T A2 from T A1. Put them in the expression. So you will put it as 1 upon T A2 plus 0 and 1 upon and ultimately you will get the same expression. So whether you look at it as sudden super heat or you look at it as instantaneous change in T A the expressions are the same. See physics will not change just because how you take it physics will remain the same there will be a change in the net lift. But over a period of time when T A1 and T A2 equalize there will be no change in the net lift which is the situation for slow change in temperature. So for a sudden shock change in temperature there will be a change in the net lift for a gradual change that changes 0.