Machines — Reversible vs Non-Reversible A machine that cannot do any work in the reversed direction (i.e., it will not back-drive when effort is removed) is called a reversible machine. True or false?

Introduction / Context:
Understanding reversibility is essential for safety and control in mechanisms such as jacks, hoists, and worm gears. It distinguishes systems that can be driven by the load from those that hold position by themselves.

Given Data / Assumptions:

• Terminology from classical theory of machines.
• Focus on whether the machine can back-drive when effort is removed.

Concept / Approach:
A reversible machine can run in reverse under load (the load can drive the machine). A non-reversible (self-locking) machine cannot be driven backward by the load, typically due to friction and geometry (e.g., small helix angle in screw jacks).

Step-by-Step Reasoning:

Verification / Alternative check:
For a screw mechanism, if helix angle α < friction angle φ, the screw is self-locking (cannot back-drive) — the opposite of reversible behavior.

Why Other Options Are Wrong:
Marking 'True' would conflate opposite definitions and can lead to unsafe design choices.

Common Pitfalls:
Assuming 'reversible' means 'reversible in control' rather than mechanical back-drivability; ignoring the role of friction angle vs helix angle.

Final Answer:
False — such a device is non-reversible or self-locking, not reversible.