Question

By logical reasoning, it should be clear that the two most used positions of the master controller on trains in regular passenger service are?

Answer 1

The two most used positions of the master controller on trains are for accelerating and braking, aligning with their primary functions. Stationary observers on the tracks experience a change in sound frequency due to the Doppler Effect, while the train's engineer hears the actual emitted frequency.

Step-by-step explanation:

The two most used positions of the master controller on trains in regular passenger service are likely to be for accelerating and braking. When a train begins its journey or needs to increase speed, the master controller will be in a position that allows the train to accelerate. Conversely, when the train is approaching a stop or needs to slow down, the master controller will be in a position that applies the brakes.

Addressing the physics concepts mentioned in the questions:

1. As a train approaches a stationary person, the frequency of the sound from the train's whistle will appear higher than when the train is moving away. This is due to the Doppler Effect, which is the change in frequency of a wave in relation to an observer who is moving relative to the wave source.
2. The frequency observed by the train's engineer traveling on the train would be the actual frequency emitted by the whistle, as there is no relative motion between the engineer and the source of the sound.