Reversible vs. non-reversible machines — definition check: A machine which is capable of doing work in the reversed direction after the effort is removed is called a non-reversible machine. Is this statement correct?

Introduction / Context:
In machine theory, it is important to distinguish between reversible and non-reversible (self-locking) machines. This affects safety, back-driving behavior, and efficiency calculations for hoists, jacks, and geared mechanisms.

Given Data / Assumptions:

• The statement claims that a machine which can reverse and do work after the effort is removed is “non-reversible”.
• Standard definitions of reversible and non-reversible machines apply.

Concept / Approach:
A reversible machine is one that, if the load is allowed to act (with effort removed), will back-drive the mechanism and return energy to the source. A non-reversible (self-locking) machine will not move when the effort is removed; friction or geometry prevents back-driving. Therefore, the statement in the stem contradicts the standard definition.

Step-by-Step Solution:
Definition: Reversible machine ⇒ capable of back-driving under load, delivering work in reverse.Definition: Non-reversible machine ⇒ cannot be back-driven (self-locking) when effort is removed.The statement describes back-driving ability, hence it matches “reversible,” not “non-reversible.”Therefore, the statement is incorrect.

Verification / Alternative check:
Examples: A low-friction pulley system can back-drive when the load pulls downward (reversible). A screw jack with large friction angle is self-locking and will not descend without applied effort (non-reversible). The behavior clearly differentiates the two cases.

Why Other Options Are Wrong:

• Yes: Accepts a definition that is opposite to standard terminology.

Common Pitfalls:

• Confusing “reversible” with “reversible thermodynamics.” Here it is purely mechanical back-drive capability.
• Assuming any high-efficiency machine is non-reversible; in fact, higher efficiency often makes back-driving easier.

Final Answer:
No