 Now, relative velocity like she said, relative velocity when it's okay, so itself, himself is going forward with these two, will not increase. Yes or no? So you feel that, who is at? Okay, so we can say that it is with respect to absolute velocity. Okay, just tell me what in this void observer subtracts its own absolute velocity from everything he sees. Such example, suppose this is observer moving forward 5 meter per second. So can you tell me the velocity of being with respect to n and why not 0? So 5, so that is positive direction temperature this way. Okay, that you need to stop moving this side 5 meter per second. Then what do you have to do? When it comes to motion in 20, there is, which is, I am going to introduce a concept with respect to example. Like say this is phi 1, this is phi 2. So velocity of approaching, so that is all other concepts of what is the strength of equation is constant. See how, so in this case velocity to increase to 2D from D, the distance between them should increase to 2D. So how much time they should take? I can show you few more concepts where you can solve various questions using. I am going one step forward where.