Pneumatic actuator Some types of pneumatic actuators include: Pneumatic actuator A pneumatic control valve actuator converts energy (typically in the form of compressed air) into mechanical motion. The motion can be rotary or linear, depending on the type of actuator. A Pneumatic actuator mainly consists of a piston or a diaphragm which develops the motive power. It keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm or piston to move the valve stem or rotate the valve control element. Valves require little pressure to operate and usually double or "triple" the input force. The
Potential energy distance at which "U" becomes zero: formula_34 and formula_35. The choice of formula_36 at infinity may seem peculiar, and the consequence that gravitational energy is always negative may seem counterintuitive, but this choice allows gravitational potential energy values to be finite, albeit negative. The singularity at formula_34 in the formula for gravitational potential energy means that the only other apparently reasonable alternative choice of convention, with formula_36 for formula_34, would result in potential energy being positive, but infinitely large for all nonzero values of "r", and would make calculations involving sums or differences of potential energies beyond what is possible