Bungee physics is energy bookkeeping with an elastic cord. You start high and still. You end hanging and tired. Everything in between is conversion between gravitational potential, kinetic, and elastic energy—plus losses.
This page is the model. The "how it feels" version lives next door.
Energy from platform to low point
At the platform you have gravitational potential energy relative to the lowest point of the jump. As you fall, that potential converts to kinetic energy—you gain speed. Once the cord is taut and stretching, kinetic energy converts into elastic potential energy stored in the deformed cord.[1][2]
At the lowest point, if you ignore losses for a moment, most of the energy that came from height is sitting in the stretched cord (minus what is still kinetic if you are not fully stopped). Reality always has losses: cord hysteresis, air drag, harness friction. Those are why you do not bounce forever.
Force and Hooke’s law as a teaching model
For an ideal spring, restoring force scales with extension: F = −kx within the elastic limit.[3] Bungee cords are not perfect linear springs for the whole ride. Stiffness can change with stretch, temperature, and construction. Still, the teaching model is useful: more stretch → larger upward force → eventually net force points up and you decelerate hard relative to freefall.
Peak loads depend on drop height, cord length and stiffness, jumper mass, and how you leave the platform. Published "average peak g" numbers on random blogs are not universal. Treat them as anecdotes unless the measurement setup is documented.
Why mass and clearance are the same problem
Heavier mass at the same height means more gravitational energy to absorb. Operators set cord combinations and free lengths so the low point stays clear of obstacles. That is why weight ranges are product-specific, not vibes. AJ Hackett’s New Zealand products publish different min/max weights for different jumps for that reason.[4]
Undershoot the minimum weight and the system may not stretch or rebound as designed. Overshoot the maximum and you shrink clearance and raise loads. Either way you are outside the design envelope.
What professional ops add beyond the textbook
Textbooks stop at ideal energy. Real ops add redundancy, daily gear checks, harness fit, weather holds, and refusal to jump when numbers do not work.[5] Physics says what the cord must do. Operations decide whether today is allowed.
If you want the rider’s view of the same timeline: why the fall feels the way it does.
Bottom line: height becomes speed, speed becomes stretch, stretch throws you back, losses end the ride. Mass and clearance are engineering, not personal judgment.
Sources
- OpenStax College Physics — gravitational potential energy
- OpenStax University Physics — elastic potential energy (½kx²)
- OpenStax College Physics — Hooke's law
- AJ Hackett Bungy NZ — FAQs (product weight ranges)
- AJ Hackett Bungy NZ — Is bungy jumping safe?
Image credits
- Photo: Dariusz Jemielniak ("pundit") / Wikimedia Commons (CC BY-SA 4.0)
- Photo: Poni Abraham / Wikimedia Commons (CC0)