The Physics of Bungee Jumping

Jesmarie Hernández Cruz

Modern bungee jumping has been an extreme activity for those in search of an adrenaline rush and excitement all around the world. This sport consists on jumping off any sort of tall structure, such as bridges or buildings, while being connected to a large elastic cord that falls vertically downward until the elastic bungee cord comes to decent to a stop, before pulling back and afterwards oscillating up and down until the energy is dissipated. The rebounds or oscillations are what give the person the thrill of the sport. Nowadays, bungee jumping has become a popular trend for many amateur jumpers, but what many enthusiasts of this sport don’t understand is the physics behind bungee jumping, and how important it is for the jumper’s safety.

Hooke’s Law of Elasticity states that the force of an elastic object uses to reinstate itself to an original length is relative to, but in the opposite direction, of the length the spring is stretched. Mathematically this law is expressed as F=-kx, where F represents the quantity of force necessary to restore elastic material to its position, k is the spring constant, x is the distance between the stretched cord to the initial position of equilibrium, and the negative sign means opposite direction and not negative value. When this law is applied to bungee jumping it basically tells us how much tension a spring can endure and the maximum length it will reach. 

It must be taken into accounts different aspects; such as potential energy, kinetic energy, elastic energy, the different forces involved (like gravity, and weight of the jumper), distance to fall, etcetera when bungee jumping is involved. Before the jump, the person is at a specific height, in which there is a certain amount of potential energy (m*g*h). Once the person jumps he enters the free falling, in which gravity is the only force acting on the motion of the body, and this is where the energy begins converting into kinetic energy (0.5*m*v2). After the free falling has occurred in a matter of seconds, the jumper now has fallen to a specific length. In this moment which the ropes starts to elongate, the kinetic energy starts to transform into elastic energy (0.5*k*x2), which is stored in the bungee cord. This elastic energy will first come from the gravitational potential energy. Both the elastic and kinetic energy will begin to grow until an equilibrium point is reached. It is then that the force of the bungee cord will begin to outbalance the weight of the jumper, and now he will decelerate. Then the jumper will have fallen at the bottom extremity of the jump, which is the length plus the distance that the bungee cord has stretched to. Additionally the velocity at that moment is equal to zero. Afterwards oscillations will then begin, pulling the jumper up and down until all the energy has dissipated and the cord will return to its original shape. 

The organizations or groups that conduct bungee jumping must take many decisions into account before providing others with this activity. For example: owning the right equipment, knowing the types and maximum lengths of the bungee cords for different falls, and it must also be taken into account the weight of the jumper (because cords do have a specific weight limit). These are all very important because they guarantee the safety of those who practice this sport, and also one way or another are indefinitely related to Physics. To conclude, Physics laws and principles helps us understand many aspects involved in the different activities that we conduct in our lives. For bungee jumping, modern physics explains and simplifies every detail involving how it occurs and why it behaves in the way it does, resulting in a much safer and more enjoyable sport for everyone participating. 

References

Giancolo, Douglas C. Physics for Scientists & Engineers with Modern 

Physics. 4th. Upper Saddle River, N.J: Prentice Hall, 2009. Print.

Taphorn, Amanda. "Bungee Jumping with Elastic Force." Physics247. N.p., n.d.  

Web. 29 Apr 2011. .