In a double-rod cylinder, what is true about the motion of the two rods?

• A. They move independently
• B. They extend at different speeds
• C. They retract at different speeds
• D. They extend and retract each rod at the same speed

Answer: (D)

In a double-rod cylinder, both rods are driven by the same piston, so they move in sync. As the piston travels, it pushes or pulls on both rods equally, meaning each rod extends by the same amount and retracts by the same amount. The speed of extension and retraction is the same for both rods because their motion is tied to the single piston’s displacement and velocity. This setup is why you don’t see one rod lagging behind or moving independently—the two ends mirror each other for balanced, simultaneous motion.