How Do You Calculate the Speed of a Bungee Jumper 19m Below the Launch Point?

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SUMMARY

The discussion focuses on calculating the speed of a bungee jumper who falls 19 meters below a launch point 53 meters above the river, using a bungee cord with a spring constant of 65.5 N/m and an unstretched length of 11 meters. The jumper's mass is 75 kg. The key equations utilized include the conservation of energy principles, specifically the gravitational potential energy (GPE) and elastic potential energy (Es). The correct approach involves using the change in height (Δh) of 19 meters for the GPE calculation, rather than the total height of the cliff.

PREREQUISITES
  • Understanding of gravitational potential energy (GPE) and elastic potential energy (Es)
  • Familiarity with the conservation of energy principle
  • Basic algebra for solving equations
  • Knowledge of spring constants and their application in physics
NEXT STEPS
  • Review the principles of conservation of energy in mechanical systems
  • Study the calculation of elastic potential energy using Hooke's Law
  • Learn about the dynamics of free fall and its impact on energy calculations
  • Explore practical applications of energy conservation in real-world scenarios
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and energy conservation, as well as educators looking for examples of practical applications of these concepts in bungee jumping scenarios.

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Homework Statement


A bungee jumper of mass 75 kg is standing on a platform 53m above the river. The length of the unstretched bungee cord is 11m. The spring constant of the cord is 65.5N/m. Calculate the jumpers speed at 19m below the bridge on the first fall.


Homework Equations


Em1=Em2 Ek=1/2mv^2 Es=1/2kx^2 GPE=mgh


The Attempt at a Solution



Find x by subtracting 11m from 19m which is 8m, this is how far the bungee cord is stretched. Use x in formula gpe=Ek+Es. Problem arises when I sub values in answer is off.
 
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Show us what you did.
 
x=19m-11m
mgh=1/2mv^2+1/2kx^2
subbed values in but didnt get right answer :S
 
What did you use for h?
 
Height of the cliff or bridge which is 53m
 
That's your problem. He hasn't fallen the whole distance yet. He has only fallen h = 19 m.
 
wait but total energy at top of the cliff is mgh where height is 53 m though
 
Try 19 m in your equations and see what you get. The equation should be mgΔh. It is the change in potential energy that matters, not the total potential energy relative to some arbitrary reference.
 

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