Demonstration: Bungee Jumping

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[[image:bungee_photo.jpg|600px]]
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[[image:bungee_photo.jpg|777px]]
  
The following second order non-linear differential equation models a bungee jump:
 
  
<math>m y''(t) + m g + b(y(t)) + \beta y'(t) = 0.</math>
 
 
Here y(t) denotes the position of the jumper at time t;  m is the mass of the jumper,  g is the gravitational constant, and <math>\beta</math> is the damping coefficient due to air resistance.
 
 
A bungee cord acts like a spring when stretched, but it has no restoring force when "compressed". The restoring force of the bungee cord b(y)  is thus modeled as follows:
 
 
<math>b(y)=\left\{\begin{array}{cc}k y,&\mbox{ if }
 
y\leq 0\\0, & \mbox{ if } y>0\end{array}\right.</math>
 
, with k being the spring constant of the bungee cord.
 
 
The animation below shows the position y(t) and the acceleration <math>y''(t)</math> of the jumper at time t.
 
 
The natural length of the bungee cord is 100 ft, and the jump starts at a height of 100 ft. The dashed line shows the equilibrium solution, i.e. the position of the jumper at the end of the jump.
 
  
 
<html><script type="text/javascript" src="http://www.wolfram.com/cdf-player/plugin/v2.1/cdfplugin.js"></script>
 
<html><script type="text/javascript" src="http://www.wolfram.com/cdf-player/plugin/v2.1/cdfplugin.js"></script>
 
<script type="text/javascript">
 
<script type="text/javascript">
 
var cdf = new cdfplugin();
 
var cdf = new cdfplugin();
cdf.embed('bungee.cdf', 692, 536);
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cdf.embed('http://helmut.knaust.info/NB/Bungee.cdf', 777, 1200);
 
</script></html>
 
</script></html>

Latest revision as of 22:16, 14 October 2013

Bungee photo.jpg


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