Bungee Jumping Physics: Minimum Height Needed

In summary, the conversation involved a person attempting a bungee jump from a bridge and the minimum height needed for the jump to be successful. The problem was divided into three parts and approached using different methods, resulting in different answers. The issue of air resistance was also discussed and the importance of properly considering the conversion of kinetic energy to elastic potential and gravitational potential was emphasized. The conversation concluded with a suggestion to start over with a new post in the forum's homework section for better and more helpful answers.
  • #1
harihrn
15
0
Um this problem involves a man jumping off a bridge with a bungee chord holding him. he weighs 102 kg and the stretch constant of the chord is 167n/m. And there is a 12N air resistance. what is the minimum height needed for him to do this? thanks! (one more thing, the length of the rope when slack is 20 ft
 
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  • #2
Have you attempted the problem yet? Please show your work.
 
  • #3
In my opinion, anything involving bungee jumping should be in a mental health forum... :oldsurprised:
 
  • #4
yes of course, i divided the problem into three parts, the initial fall till the rope starts to stretch, then the stretch
the Ke value that i came up with was mgH, and the sum of the energies is KE-W, which was mg(6.09) -12(6.09). 6.09 m is the length of the chord when it is slack (20ft). the sum of the energies came up to be 6014.484 joules. I then set that equal to 1/2kx^2 12x, which became a quadratic equation: 83.5x^2+12x-6014.484, x being the amount it should stretch, which came up to be about 8.42 meters. The minimum height that i found was 14.51 meters
 
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  • #5
Im not sure whether my approach was right in the first place, since another method that i tried gave me a different answer.
I set mg(height of the bridge)= 0.5kx=(height-the length of chord/rope)^2 which gave me 22.3 m.
 
  • #6
Do you have multiple personality disorder, or did you quote yourself by accident? :D

I'm sorry. I know that you are serious about the subject, and other folk like Nathanael will help you. I was just temporarily bored and couldn't resist the urge. I promise that this was my last interruption of your thread.
 
  • #7
my bad I'm new to this lol
 
  • #8
I agree with your first approach. The reason the second method gives a different answer is because it neglects air resistance.

Danger... :DD
 
  • #9
there is another way i did it and it gave me ANOTHER answer, lol i must sound annoying, but i watched a simulation which showed that when the chord is fully stretched, the kinetic energy during the fall converts to elastic potential and gravitational potential. so, i set the KE = mgx+0.5kx^2, x being the distance it is stretched, and i got 4.4 as the answer for the stretch, and the total height came out to be 10.49m. IDK which one to go with
 
  • #10
i really need some help
 
  • #11
harihrn said:
which showed that when the chord is fully stretched, the kinetic energy during the fall converts to elastic potential and gravitational potential.
If the rope is stretched and the person is moving upwards, then the KE will be converted to elastic PE and gravitational PE
But if the person is moving downwards (like in our situation) then the GPE and KE will be converted to elastic PE.

Imagine if there was no rope (and so no elastic PE). If the person is moving upwards, KE is converted to GPE. But if the person is moving downwards, GPE is converted to KE.
 
  • #12
so what would be the conceptual formula that i should use? like which method of the ones that i did is right?
 
  • #13
OK, everyone... Stop it now.

Harihrn, start over again with a new post in the introductory physics homework section of this forum, and use the homework template to organize your thoughts and let us know what you've already figured out. You will get much better and more helpful answers that way.
 

Related to Bungee Jumping Physics: Minimum Height Needed

1. How does gravity affect the minimum height needed for bungee jumping?

Gravity plays a crucial role in determining the minimum height needed for bungee jumping. The force of gravity pulls the jumper towards the ground as they fall, and the bungee cord stretches to slow their descent. The minimum height needed for bungee jumping is directly related to the strength of the bungee cord and the weight of the jumper, as these factors determine how far the jumper will fall before the bungee cord reaches its maximum stretch.

2. What is the formula for calculating the minimum height needed for bungee jumping?

The formula for calculating the minimum height needed for bungee jumping is h = (2mgl)/k, where h is the minimum height needed, m is the mass of the jumper, g is the acceleration due to gravity, l is the length of the bungee cord, and k is the spring constant of the bungee cord. This formula takes into account the weight of the jumper, the strength of the bungee cord, and the force of gravity to determine the minimum height needed for a safe and successful bungee jump.

3. How does the length of the bungee cord affect the minimum height needed for bungee jumping?

The length of the bungee cord is a crucial factor in determining the minimum height needed for bungee jumping. A longer bungee cord allows for a greater distance for the jumper to fall, which means a higher minimum height is needed for a successful jump. On the other hand, a shorter bungee cord requires a lower minimum height, but it also means a shorter fall and less time for the cord to stretch and slow the descent.

4. What other factors besides gravity and the bungee cord affect the minimum height needed for bungee jumping?

Aside from gravity and the bungee cord, there are other factors that can affect the minimum height needed for bungee jumping. These factors include the weight and size of the jumper, the design and elasticity of the bungee cord, and the location and environmental conditions of the jump site. For example, a heavier jumper may require a higher minimum height, and a bungee cord with a higher spring constant will allow for a lower minimum height.

5. Is there a minimum height requirement for bungee jumping to ensure safety?

Yes, there is a minimum height requirement for bungee jumping to ensure safety. This minimum height is determined by various factors, including the weight and size of the jumper, the length and elasticity of the bungee cord, and the force of gravity. It is essential to follow this minimum height requirement to ensure that the bungee jump is safe and does not result in injury to the jumper.

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