Final answer:
The teacher's velocity is 1 m/s after walking a net displacement of 50 m in a total of 50 seconds up and down a hallway.
Step-by-step explanation:
The student asked about calculating the teacher's velocity after performing a certain movement in a hallway. To determine velocity, we use the formula velocity = displacement/time. The teacher first walks 50 m down the hall and then 100 m up the hall, which results in a net displacement of 50 m (100 m - 50 m). The total time taken for the journey is given as 50 s. Therefore, the velocity of the teacher is displacement divided by time, which equals 50 m / 50 s, resulting in a velocity of 1 m/s.