"A 20 kg block, m1, is sliding on a 10 kg block, m2. The blocks are on a 20º slope and are connected by a light string looped over a pulley. " All surfaces are frictionless and the string/pulley are massless. I understand that the 20kg block should slide down since it should have a greater force. When I draw the diagram I have three forces for each block. The normal force perpendicular to the incline, weight pointing straight down and the tension from the String. I'm however confused on certain aspects of the diagram. For instance Tension should always be along the string... so does that mean the tension vector for each block should be in opposite directions? Also since the 20kg block is sitting a top the 10kg block does that not add to the magnitude of the 10 kg's block weight force? Thanks for any help in advance.