I am having a hard time understanding this concept... I understand Rectilinear motion consists of a line and Angular Motion is of a Angle. But I cant seem to understand how to use this for problem solving. I have two examples here that I will give and I have the answers but I cant seem to figure out how to solve them. 1. An automatic pipewelder can weld 40in/min. How long does it take to complete one pass around a pipe 4ft in diameter. *ok first thing i do is convert the 4ft into 48 inches to make it all one unit. Then I simply divide 48inches into 40in/min and its simply 1.2min, The book has 3.77min as the answer so I am assuming I have to use the angular of the pipe but man im stuck on that. 2. By means of a stroboscope, the speed of a puller 200mm in diameter is found to be 1600 rpm. Determine the speed of the belt passing over this pulley.. Ok the answer is 16.7m/s. I have no idea how to seriously solve this....not even a start really. I am assuming the equations s=r*angle v=rw alpha=rbeta are the questions I need, but man I cant seem to get any of this stuff. I need a breakdown of this please.