• Support PF! Buy your school textbooks, materials and every day products Here!

[Mechanics] Tension in bungee jumping

  • #1
12
1

Homework Statement


A bungee jumper of mass 60kg jumps from a bridge 24 m above the surface of the water. The rope is 12 m long and is assumed to obey Hooke's law. What should the spring constant of the rope be if the woman is to just reach the water?

Homework Equations


Ep=mgh
E=1/2 kx^2

The Attempt at a Solution


Energy conservation? I'm definitely doing something wrong here and not understanding something but I don't know what.

mgh = ½kx^2
(60)(10)(12) = ½k(12)^2
[I put the length of the unstretched part of the rope as my h value and x as the extension, which is 24-12=12]

k= 100 Nm^-1
[This is the answer I got]

But the answer is k=200 Nm^-2
 

Answers and Replies

  • #2
Doc Al
Mentor
44,892
1,144
I put the length of the unstretched part of the rope as my h
To calculate the initial gravitational PE, use the height above the water.
 
  • #3
12
1
To calculate the initial gravitational PE, use the height above the water.
okay thanks!
 
  • #4
13
1
This is the key statement : The woman jumps from a bridge 24 m above the surface of water.
 

Related Threads on [Mechanics] Tension in bungee jumping

  • Last Post
Replies
5
Views
8K
Replies
2
Views
3K
Replies
11
Views
7K
Replies
1
Views
837
Replies
3
Views
4K
Replies
2
Views
5K
Replies
13
Views
8K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
8
Views
8K
Top