Introduction

One question that every student has wondered at some point in their schooling is, “When am I ever going to actually use this stuff?” The Science of Riding a Zip Line website serves as one answer to that question. Its purpose is to demonstrate how the Science, Technology, Engineering, and Mathematics (STEM) principles that you have learned apply to real-world situations. No matter what your age or grade level may be, The Science of Riding a Zip Line website will help you understand the science and engineering principles related to calculating your maximum speed while riding a zip line.

Photos of two zip line riders

Design of a Zip Line

Every zip line consists of a trolley attached to a steel cable that is typically covered with a vinyl coating. Gravity propels the rider from start to finish.

The first step when designing a zip line is to identify the parameters involved. Some of the questions that need to be answered are:

    • How long of a distance will the zip line span?
    • How high should the start and end points be?
    • What will the start and end points be attached to and how can they be secured?
    • How much slack should there be to give the zip line an appropriate slope?
    • What will the weight limitations be?

* WARNING: Always consult with an industry professional before attempting to design your own zip line.

The zip line illustrated below covers a horizontal distance of 255 meters (m) and has a vertical drop of 16 m to the lowest point. The start point is 13 m above the ground and the end point is 11 m above the ground. Both points have been securely anchored using trees. Notice that the topography of the ground has a slightly downward grade from the start point to the end point. This helps achieve a sufficient slope, approximately 4 degrees in this example, without causing the cable to be extremely high off the ground at the start point. For safety reasons, a weight range of 70 to 250 pounds is acceptable for a zip line this size.


Zip line diagram

Figure 1. Measurements for the last zip line on the WVU Canopy Tour. The drawing is not shown to scale.

As a recreational activity, riding a zip line only takes the courage to step off the platform. On a ride of approximately 300 m in length, your maximum speed might approach 48 km/h (30 mph). On a longer ride, say of 900 m, your maximum speed might approach 96 km/h (60 mph).

Our competitive nature makes us want to go as fast as possible regardless of the distance of the zip line.



Activity

Listen to the trolley going over the cable. Can you hear the change in frequency as the trolley accelerates? Can you tell when the trolley has passed the lowest point on the cable and begins to decelerate?