Welcome to our channel It Fills His Body. We are trying to explain physics in simple words and our first lecture series is based on Einstein's relativity. Our first class is known relativity before Einstein's contribution and that is the Galilean transformation where two referring sphere one is a prime and there is a s is relative to each other sorry our relative to each other and a motion between them is v and an s-prime frame is moving with velocity v in the direction of x prime of x and in this relation sorry in this Galilean transformation this is the simple Galilean transformation with Einstein it was the only transmission equation and it is valid only on only one when the motion is not compared to speed of light now hence the transformation equation or relations will be if we consider a point x y z according to s and x prime y prime z prime according to a prime so the transformation will look like x prime equals to x minus v t and there the time is same because in before Einstein's contribution our lorins contribution time was university so and the another axis will be y prime equals to y and z prime equals to z this is called the Galilean transformation but this transformation equation is not valid for a light and it is only when the motion is non-gletivistic or motion is not compared to speed of light there is also inverse transmission you can transform the set of point from x prime to s and that will look like this x equals to x prime plus v t equal to 2 prime and y equals to y prime and z equals to z prime that is called the inverse Galilean transformation now the velocity addition before Einstein's contribution we move that from Galilean transformation we can say that velocity is added the relative velocity is added but in the activities it is not linear and the activity it is so complete if we consider a point in a point a particle is moving in a prime prime is x prime y prime and z prime and the s prime in s frame the point is x y and set the location of the point is x y and set x prime is x y and z so the particle velocity will be from we can write at first the Galilean transformation x prime equals to x minus v t y prime equals to y and z prime equals to z and t prime equals to t we can taking the derivative in this both sides with respect to time t then we can obtain the velocity addition equation for non-derextic cases so taking d dt or the derivative with respect to time the equation looks like so d dt of x prime equals to d dt of x minus v and d dt of t and d dt of y prime equals to d dt of y now if we take the d dt of x prime as y sorry u prime equals to u minus v where u is the d dt of x this is the x direction so we can write x in this of x so a motion in y direction will be will u prime y equals to u y now in z direction d dt of z prime will be equals to d dt of z so in z direction the velocity will be y's sorry u z prime equals to u z so this equation is known as the velocity addition where it is so simple and linear equation we can write the equation again u x prime equals to u x minus v is known as velocity addition equation or this is the relative velocity of the particle which is moving in a prime frame and if one looks from s frame the velocity will be u x in our next video we'll show that for light this equation is not correct the light is not added the speed of light is constant for all reference frame so okay thank you for watching this video and stay with us share this video and like this video and if you have any confusion then comment in the box so