Which of the following is an example of mechanical failure?

A belt breaking on a conveyor system is an appropriate example of mechanical failure because it directly relates to the physical components of machinery or equipment that are designed to perform a specific function. Mechanical failure typically involves the breakdown or malfunction of mechanical parts due to wear and tear, fatigue, or other physical conditions affecting their integrity.

In this case, the conveyor belt is a critical part of the system responsible for transporting materials. When it fails, it disrupts the entire process, indicating a mechanical issue. This type of failure is often characterized by a sudden failure of a mechanical component that impacts operational efficiency.

The other options may involve problems encountered during operation or issues relating to performance, but they don't exemplify a mechanical failure in the same direct way. A leaking pipe, for example, points more to a failure in sealing or material integrity rather than the mechanics of the system itself. A valve malfunction could involve mechanical aspects, but it often relates to issues like blockage or improper function that are not purely mechanical in nature. Similarly, a clogged filter is usually a maintenance issue rather than a mechanical failure related to the components themselves breaking down.