What is one reason why circular motion might be difficult to achieve with pneumatic systems?

Pneumatic systems generally operate through the control of pressurized air, which often results in linear motion. This is because pneumatic actuators, such as cylinders, are designed to create straight-line movement as the air pressure pushes the piston in a back-and-forth motion. While it is possible to achieve circular motion using additional components like rotary actuators or specific configurations of linkage systems, the fundamental operation of most pneumatic devices revolves around linear motion. Therefore, the inherent design and functionality of pneumatic actuation make it more straightforward to produce linear rather than circular motion, which is why this option accurately describes the challenge of achieving circular motion in pneumatic systems.