Abigail Durling

Bungee Jumping

Bungee jumping originated hundreds of years ago in New Guinea. Men leaped from very tall wooden towers attached to the tower by vines tied to their ankles, it was originally used as a test of courage but has since been converted into a recreational activity and is seen to be a once in a lifetime thrilling experience. The sport is simple yet exciting; jumping from a tall platform i.e. a bridge or a crane whilst attached to a length of elastic chord.

A lot of calculations must be done before a bungee jump to ensure the safety of the jumper. The chord must be exactly the right length to give the best (yet safest) possible experience. If the chord is too short the jumper may not feel the optimum thrill however if the chord is too long it would probably result in the jumper being killed as they would hit the floor (go splat).                                                    I am going to do an experiment in order to find the exact height a fixed weight figure would need to jump from - with a certain length chord - in order to stop them just before they hit the ground.

One way to try to work out the correct launch height would be to use the laws of motion; The rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction, this would be difficult however as the force on the jumper is not the same throughout the jump, the tension varies with extension. Instead we could use energy conservation. The jumper will lose and gain energy in different stages of the jump. When the jumper reaches the very bottom of the jump his kinetic energy is ‘0’. This energy gets transferred to the chord as it stretches giving it elastic energy (Eel). ‘Energy conservation tells us that the GPE lost must be equal to the elastic energy gained by the rope’ (Salters Advanced Physics AS)

Before I start I must take air friction into consideration, as the jumper falls through the air they will experience air resistance slowing them down slightly. However this air resistance is likely to be very small compared to the opposite forces, as well as this it would be far too difficult for me to factor in air resistance in the science labs and I can therefore ignore it. I should also think about the motion of the jumper during the fall, they are likely to have both vertical and horizontal motion, the experiment will be much easier to understand fully if we are able to ignore one of these dimensions which is why I shall be focusing on the vertical motion alone.

Preliminary

In order to calculate the height I must conduct a preliminary experiment to find out the extension of a 0.5m chord with a range of loads.

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Equipment

  • Elastic chord – Gold-Zech elastic
  • Plasticine
  • Scales accurate to 0.01g
  • Meter rulers accurate to 1mm
  • Permanent marker
  • Flat surface (desk)
  • G. Clamp
  • Clamp

Method

  1. Weigh Lego bungee model.
  2. Decide a range of masses to test of which the mass of the figure is somewhere in the middle.
  3. Weigh out plasticine into the range of masses making all into a ball.
  4. Set up apparatus as shown above.
  5. Using the first mass let it hang on the chord. Measure from the top of the plasticine ball, at eye level, the ...

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