As showm in figure stationary force (MG) applied on two pulleys. Force is not moving. Pulleys can rotate about their axis. We simply do force analysis. Mg will equally devide and applied on each pulley in vertical downward direction. This MG/2 further devided in two parts. One is tengential and second is towards the center. Tengential part will help to rotate the pulley and towards the center part will generate friction. So force is not moving and it can help to rotate pulley.







