# 3 questions about Bungee jump

1. Oct 15, 2008

### kittychg

Hi everyone! I am recently doing an assignment for my broadening course. But I really dunno how to answer these questions as I only have basic knowledge for physics. Could anyone help me out? The questions are as follow:

1. Explain why iron chain is not used as bungee jump string instead of an elastic cord.

2. If two identical bungee jump strings are tied to the jumper instead of one bungee jump string, what is the effect on the time for the jumper to bounce up from the minimum point to the equilibrium point for the first time? You may assume that Hooke's law is valid in the mentioned strings.

3. John says, 'It is safe to use a bungee jump string which can only provide a maximum tension (restoring force) just equal to the weight of person.' Comment on John's statement.

Thanks again for help :]

Kitty

2. Oct 15, 2008

### tiny-tim

Welcome to PF!

Hi Kitty! Welcome to PF!

Show us what you've tried, and where you're stuck, and then we'll know how to help.

3. Oct 15, 2008

### kittychg

I have thinked about it and come up with some ideas.

Question1 should be linked to elasticity. As iron chain has less elasticity, it may exert greater force on the bungee jumper and cause damages to his body.

Question2 is related to hooke's law but i don't reli understand what it is about.... I guess that the time would be halved as their will be two acting forces??

Question 3..... the claim by John should be wrong, as their will be additional gravitational force. So when the string extents in length, the total force would be so great that the string will break.

Um.... I think that my answers sound a bit strange :(

4. Oct 16, 2008

### tiny-tim

Hi kittychg!

How detailed is the physics in your broadening course? Have you done Newton's second law , or Hooke's law ? Have you done force diagrams ?

5. Oct 16, 2008

### kittychg

Yeah I did learn about the forces thing but it's a few years ago already. So I don't reli remember how to apply it....
I think the assignment is asking for preciseness, as there is word limit on each question @@

Q.1 70 words
Q.2 60 words
Q.3 60 words

Acatually is my direction to the answers correct?

6. Oct 17, 2008

### tiny-tim

1. You've only used one-third of your allowance, so talk about the height he will fall, and the velocity he will reach, and how the suddenness affects the acceleration.

2. Use Newton's second law and a force diagram to work out exactly what the answer is.

3. Add the forces to find the total tension, and do it at different parts of the fall.