Investigating the Physics of Bunjee Jumping

Investigating Bungee Jumping

By Justine Hyu

Abstract: The association of Hooke’s law with elastic were investigated by hanging masses off an elastic cord, and measuring the extensions. A graph of the results was made to determine Hooke’s constant which would later be applied to certain calculations. Then a model bungee jump was created to measure the motions and energies involved with bungee jumping. From the results gathered, calculations and predictions were made in order to provide the foundation of the construction, and properties of real bungee cords which could be applied when jumping off the Story Bridge.

Aim: To investigate the factors and properties associated with a bungee cord, in order to design a suitable model bungee jump, which will be applied as the basis for an actual bungee jump attraction on the Story Bridge.

Introduction and Background Information:

This investigation into bungee jumping was initiated as a result of a company’s proposal to construct a bungee jump attraction on the Story Bridge. Bungee jumping is a popular extreme sport which originated from the Pentecost Islands of Vanuatu, where the men tied vines around their ankles and jumped from a height as a test of courage. Today bungee jumping consists of an elastic cord secured to a platform and a variety of other equipment. Modern bungee jumping, with an elastic cord, demonstrates Hooke’s Law and consists of a variety of energy transformations. According to Hooke’s law the spring constant is theoretically linear, and is calculated by k=F÷, therefore is the gradient of the line which passes through the origin.

There are many important variables to consider when designing a bungee jump such as Hooke’s (spring) constant, mass, weight, length of the chord, the length of extension, height, force, velocity, acceleration, gravitational potential energy, elastic potential energy and kinetic energy. Each of these factors contributes to, and affects different aspects of the bungee jump, but together can impact the overall effectiveness.

When applying the model to real life it is important to know the Hooke’s constant as further predictions and calculations can then be applied to determine other variables such as the appropriate length of the chord, the extension and force. Length, extension and force are extremely crucial because if the person is too heavy the elastic will extend too much, if the person is too light the jump will be jolty and possibly cause injury. Therefore extensive planning and research has to be conducted in order to design an effective model, which could then be applied as the foundation for the Story Bridge bungee jump. Hooke’s Law is the relationship between the force exerted on a spring or elastic and the extension.

Apparatus:

elastic
Masses 50-500g
Mass holder
Stand
Ruler
Plastic Container Lid
Tripod
Glx motion sensor on person mode
Data Studio
Bench
Block

Procedure:

Two experiments were conducted in order to find basic measurements and data involved in calculations. The first experiment was carried out to find the extensions of the elastic for various amounts of mass, with the purpose of determining Hooke’s (spring) constant. Firstly, a strand of elastic was halved and tied together to produce a chord with two parallel elastics. The elastic was then secured onto the pole extension of the stand, and the length of the resulting elastic was then measured. The stand was placed on a bench with the string hung over the ledge. Masses of 50g to 500g were placed onto the mass holder, which was also measured, and then hung on the suspended string. The length between the top of the string and the bottom of the mass holder was measured for each new mass. From the recorded data, the extensions of the string was calculated and a force-extension graph was produced in order to calculate Hooke’s constant, which was the rate of change in force needed to extend the string per metre.

After the findings of the first experiment were recorded, the second experiment was carried out using the same elastic to record the motions of a bungee jump. A mass of 300g was attached to the elastic cord and secured with blu tac, and the motion sensor was put on the ground directly underneath the suspended string. The motion sensor was placed on a block under a tripod for equipment safety, and the block was utilised to ensure that there was no interference between the tripod and the sensor. A plastic container lid was secured with blu tac on the bottom of the masses to maximise the surface area and prevent other objects interfering with the sensor. Blu tac was positioned on top of the masses, to secure the masses during the fall. After the equipment was made secure, the 300g mass was brought up to the pole extension, where the string was secured. The motion sensor was initiated and the 300g mass dropped. A position-time graph was obtained from the GLX motion sensor using Data Studio.