In mechanical systems, which of these is a common example of a safety device?

Braking systems are designed specifically to enhance safety in mechanical systems. They provide a means to slow down or stop machinery safely, which is critical in preventing accidents and ensuring the safety of both operators and equipment. In vehicles, for instance, the braking system integrates various components such as brake pads, rotors, and hydraulic systems to effectively control speed and stop when necessary.

While fuel systems, exhaust systems, and propulsion systems are essential for the operation of machinery or vehicles, their primary functions do not focus on safety. Fuel systems are designed for delivering fuel efficiently, exhaust systems manage emissions, and propulsion systems provide the necessary force for movement. Therefore, these systems do not serve as safety devices in the same capacity that braking systems do.