# I What spring constant would I need to jump my height

Tags:
1. Mar 9, 2016

### Physer

In my springs what would the spring constant need to be If I am 1.8m tall and I weigh 68 kg

2. Mar 9, 2016

### Staff: Mentor

Welcome to the PF.

You probably need to be a lot more clear on what you are asking before we can provide much help. What exactly are you asking? Can you upload a diagram of what the setup would look like? Are you wanting to bounce on a spring from some height or something?

3. Mar 9, 2016

### Physer

Thank you.
Lets say I have shoes that have springs on them. My goal is to find the spring constant on my springs to jump my height. The only thing given is my weight and my height to achieve the jump

4. Mar 9, 2016

### Staff: Mentor

Having springs on your shoes won't help you unless you pump up some jumps, or drop from some height. How do you envision making this jump?

Also, is this for a schoolwork assignment?

5. Mar 9, 2016

### Physer

Yeah, its a hypothetical question. Dont know how I would approach this

6. Mar 9, 2016

### Physer

Basically I would jump Like I would on a trampoline but with shoes

7. Mar 9, 2016

### Staff: Mentor

So you would basically be pumping them up with several jumps in a row. If you have a look at this wikipedia page: https://en.wikipedia.org/wiki/Spring_(device) you will get a lot of info about springs.

One quick way to start calculating it would be to equate the energy in the fully-compressed spring to the energy it takes to lift you to the height you want. To raise your center of mass by a height h, it takes the energy E = m*g*h, where m is the mass in kg, g=9.8m/s^2, and h is the height in meters.

The energy in a compressed spring is E = 1/2 * k * x^2, where k is the spring constant and x is the distance that the spring is compressed.

Can you work with those equations to start to figure out what spring characteristics you need (spring constant k, uncompressed length, compressed length)?

8. Mar 9, 2016

### Physer

So Looking at the equations given, I think I would Find E, find a distance for the spring to be compressed, then plug it in the compressed spring equation and isolate K to find the constant?

9. Mar 9, 2016

### Staff: Mentor

Something like that. It may take some iterating to get close to the real spring parameters. You can start with what might be a reasonable compression distance (maybe half a meter?), and the fact that there are two springs (I assume) and one of you...

10. Mar 9, 2016

### Physer

Since i plug in E= mgh to E =1/2kx^2. How would i know i Jumped my height

11. Mar 9, 2016

### Staff: Mentor

I'm not sure I understand your question. It's a conservation of energy type of situation. If you are standing on a compressed pair of springs and their combined energy is the same as is required to raise you to the height h, that's what they will do...

BTW, you need to include some other factors. Like, if you want the springs to be able to bounce you to a height h above where you are when you are not bouncing, that's a bit different from the case where they raise you to a height h above where you are when you are at the fully-compressed bottom of your bounce... It would help you to start making some sketches showing positions of yourself and the springs at different parts of your bouncing...

12. Mar 9, 2016

### Physer

How i wanted it to be

#### Attached Files:

• ###### 1457563092405-1027776672.jpg
File size:
24.3 KB
Views:
69
Last edited by a moderator: Mar 9, 2016
13. Mar 9, 2016

### Physer

A quick sketch

14. Mar 9, 2016

### Physer

For the E=mgh question what would I do with E?

15. Mar 10, 2016

### Staff: Mentor

If you plug mgh in for E in the spring equation, you don't do anything with it. It just goes away. Is that what you were asking?

16. Mar 10, 2016

### Fervent Freyja

Other factors? What happens when this man loses his balance and falls? I can see him having having a blast bouncing all around -getting really, seriously into it- and then suddenly, flinging himself in all sorts of directions on accident- what are the consequences for his skull starting 12 feet in the air heading for hard pavement, you have the numbers? I don't think this is a real great plan...

Physer, if you are really going to do this, please wear a helmet and practice before jumping right into it. It sounds like fun for sure, but it could be dangerous... Working on your motor skills may help a heap!

17. Mar 10, 2016

### Staff: Mentor

Words of wisdom right there.

18. Mar 10, 2016

### 256bits

Try with a Pogo stick first to practice and get good at jumping on a spring.

19. Mar 10, 2016

### 256bits

I think, make sure there is a video for You Tube.
Watch it go viral.
People just love seeing the crazy antics of others and feeling their pain.

20. Mar 10, 2016

### A.T.

This is too unstable to bring you very high. You need something like this: