In replacing a cylinder, if the pressure and flow rate remain constant, how will a larger rod diameter affect extension and retraction?

When replacing a cylinder with one that has a larger rod diameter while maintaining constant pressure and flow rate, the dynamics of extension and retraction are influenced by the increased area of the rod.

During the extension phase, the larger rod diameter means that the effective area for fluid flow is reduced because more of the cylinder's area is occupied by the rod. This results in maintaining speed while extending because the force needed to extend the cylinder will still be present, but the increased rod diameter causes less fluid volume to control at any given moment. Hence, the extension will happen at the same speed.

On the other hand, during retraction, the larger rod diameter does not significantly compromise the flow through the back side of the cylinder (where the rod is retracting into), allowing for a quicker retraction speed. The presence of a larger rod does not impede flow as the fluid returning to the cylinder can move quickly, leading to faster retraction.

In summary, while the extension occurs at the same speed due to limited area for fluid to act on, retraction can happen at a higher speed, thus justifying the classification of the retraction speed as increased while the extension speed remains constant.