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.