Wave Motion: Elevator Constructor Q&A

[denni89627]

I work as an elevator constructor. part of an installation involves installing a steel tape the entire length of the shaft. it is very thin (imagine steel duct tape) and is under spring tension to keep it from moving too much. when at the top of the shaft i pulled the tape and sent a wave down the tape. it distinctly bounces up and down the entire length of the shaft a few times and makes a really weird star wars like sound. it starts out high pitch but ends as a low bass rumble. is the sound based on the length of the tape before and after the wave? almost like frets on a guitar? also i was wondering if the wave moves faster on the way down and slower up due to gravity or varying tension?

 

[Tide]

The dynamics are very similar to a vibrating string where the speed of a wave depends on the tension. Since the tension is greater near the top the wave travels faster there than it does near the bottom but, at a given level, the speed is the same whether the waves is ascending or descending. Transit time from top to bottom will be the same as the transit time from bottom to top - given that nothing else (such as the length) changes in the process.

 

[charng]

I find this observation about wave motion in an elevator shaft very interesting. The phenomenon you described is known as a standing wave, where the wave bounces back and forth between two fixed points, in this case, the top and bottom of the shaft. The sound you hear is a result of the vibrations of the tape, which is similar to the vibrations of a guitar string when plucked.

The pitch and frequency of the sound are indeed related to the length of the tape before and after the wave. This is because the length of the tape determines the wavelength of the standing wave, and the shorter the wavelength, the higher the pitch of the sound.

The varying tension of the tape can also affect the speed of the wave. In general, the wave will travel faster in areas with higher tension and slower in areas with lower tension. However, the effect of gravity on the speed of the wave is negligible in this situation, as the tape is under spring tension and is not affected by gravity to a significant degree.

Overall, your observation provides valuable insights into the behavior of wave motion and how it can be affected by various factors such as tension and length. Thank you for sharing your experience as an elevator constructor and for sparking scientific curiosity in this area.