When M is initially running, what is the result of pushing S2?

When M is initially running, pushing S2 results in M stopping immediately because S2 is designed as a stop control for the system. Typically, in electrical and mechanical systems, a stop switch or a similar control mechanism can bring a machine or equipment to a halt instantaneously when activated. This is essential for safety reasons, allowing operators to quickly stop machinery in case of emergencies or adjustments needing to be made.

In this scenario, pushing S2 effectively signals M to cease its operation without delay, thus ensuring immediate action is taken to prevent any potential hazards. Understanding the function of stop controls like S2 is critical for operating machinery safely and effectively.