This lecture covers the derivation of the speed distribution of a two-dimensional ideal gas by starting from a one-dimensional velocity distribution and performing a suitable coordinate transformation. The process involves deriving a two-dimensional distribution of velocities, exploring polar coordinates, and understanding the fluid dynamics. The lecture also discusses the deposition of gas molecules on a rotating drum, illustrating an experiment for measuring the Maxwell-Boltzmann distribution. Various concepts such as flux of molecules, distribution of deposited molecules, and the impact of drum rotation on molecule deposition are explained in detail.