Which condition must be satisfied for a machine to be considered self-locking?

For a machine to be classified as self-locking, it must be able to prevent motion under the influence of the load when no effort is applied. This typically occurs when the force required to move the load (the load force) is greater than the force applied through effort (the effort force) when the machine is not in motion.

In a self-locking machine, if the effort is less than the load, the machine does not allow for motion; instead, it remains at rest. This characteristic is crucial for applications such as hoists or brakes, where it is important that the system will not inadvertently lower a load or allow movement under the weight of the load alone.

This principle demonstrates that maintaining a relationship where the effort is less than the load ensures stability and control, effectively allowing the system to "lock" itself in place.