Can enough helium filled balloons make you leap to great heights?

Factual Questions
1

We’ve all heard the story of the guy who used a lawn chair to soar quite high, I’m wondering if you could use balloons to magnify your jumping height. I would think not. If you use too much helium, you just float, use too little and you you come right back down without much benefit. I guess you’d have to use an amount of helium that slightly exceeds the the minimum amount to cause weightlesness.

I ask this on behalf of a friend (seriously) who wants to make a sturdy vest of some sort that would allow him to “jump 20 feet in the air”. Any figures on how many cc’s of helium required to lift a 175lb man?

My thinking says that if you could defeat the slack in the line caused by leaping, and get 20 feet off the ground, you’d just keep floating. The BB gun method of releasing gas could work to a point, but then you’d have to tie a new balloon on each time you ascended right?

Any feasability and logistics input would be appreciated.

2

let us know how much fun it was

3

These guys think so.

4

Air has bouyancy too, just like water. If you make your density closer to that of air, via helium balloons or something else, you should be able to jump higher, even if it’s not enough to float.

5
      • It would work, but you’d need almost as much as you’d need to life the person’s weight. And although I would personally like to try it myself, I’d want to do it indoors somewhere like an airplane hangar --somewhere with no wind…
        ~
6

If you attach a large (and it will be very large) number of helium balloons to yourself so that their buoyancy cancels out a significant proportion of your weight, you will indeed be able to jump a lot higher; the slack in the line isn’t really relevant because the balloons will accelerate upwards to take it up, then they will ‘tug’ you upwards a bit.

But moving sideways is going to be a real effort, partly because you have to take a huge string of balloons with you (and overcome their air resistance), but also because your reduced (apparent) weight means you will have a hard time getting any traction.

7

This, of course, is quite wrong. When you jump up, you accelerate upwards quite faster than the balloons would accelerate if you just let go of them so, in fact, the line will become totally slack and you will get no help with your jump. You can try it with any balloon, no matter how small. The line goes totally slack.

8

Yes, the line goes slack, allowing the balloons to rise a little (accelerating faster than they would if the line was pulled tight by the suspended weight).
When the weight falls and the line goes tight again, the balloons are travelling upward at a greater rate than they would be if the line had been kept tight, so they end up ‘tugging’ and imparting a little more upward force to the suspended weight.
I’m not suggesting that the system is efficient, but the effect is real nonetheless.

I have tried this with balloons and weights; observation was the basis of my statement.

Another way to look at this is to attach the balloons to a loop of slack line; pay this out all at once and the ballloons accelerate upwards freely, when they reach the limit where the line is pulled tight, they will exert an upward ‘tug’ that is greater than the normal upward force when the whole thing is at rest.

9

Think again. Yes, you can use any upward force to jump higher.

>> If you use too much helium, you just float, use too little and you you come right back down without much benefit. I guess you’d have to use an amount of helium that slightly exceeds the the minimum amount to cause weightlesness.

No, there are other factors involved, as you will see, but any upward force will help you jump higher. There is a range between “too much” and “too little”. That’s why we have math: to calculate and measure things.

>> I ask this on behalf of a friend (seriously) who wants to make a sturdy vest of some sort that would allow him to “jump 20 feet in the air”. Any figures on how many cc’s of helium required to lift a 175lb man?

A “vest” will not do. You need a “harness” similar to what rock climbers and parachutes have.

>> My thinking says that if you could defeat the slack in the line caused by leaping, and get 20 feet off the ground, you’d just keep floating. The BB gun method of releasing gas could work to a point, but then you’d have to tie a new balloon on each time you ascended right?

The only thing you got right, in spite of wjat others have said, is the “slack in the line” thing but that can be dealt with, as you will see.

>> Any feasability and logistics input would be appreciated.

Ok, tighten your belt and get ready:

The Earth pulss you down with a force of, say, 180 lbs. If you have a harness pulling you up with exactly the same force then you just hover in place without moving. This is what happens when you hang from a beam. But imagine a constant upward force that exactly cancelled your weight, like if you had a rocket. Then if you jumped up you would just keep going up except slowed dow by air friction. But, if we neglect to consider air friction, if the rocket makes your apparent weight 1/2 then you can jump twice as high, if it makes it 1/3 then you can jump 3 times as high, if it makes it 1/4 then you can jump 4 times as high, and so on.

So, if you can normally jump up 3’ and want to jump up 12’ then you need to reduce your weight by 3/4. In other words, if you weigh 180 lbs then you need a rocket pushing you up with a force of 125 lbs.

Now, a rocket is not practical or easy but we can find simpler ways of exerting a constant or quasi-constant upward force. Bungee cord of sufficient length is one way. We have said the range is 12’ so if the total length of the bungee is 250’ the difference in force is not going to be much. (I am using a factor of 20 but you could use much less and still get good results) So all you have to do is:

1- Build bungee cord which will stretch by 1/20th with a weight of 125 lbs.

2- Build helium balloons which have a bouyancy of 125 lbs plus the weight of the bungee cord.

3- Tether the balloons to your harness using the bungee cord

4- Enjoy the jumping until the wind or something else spoils the fun.
Now, think about it, the bungee cord does not need the balloons at all, all it needs is an upward force. The bungee cord is more important than the balloons. You could hook the cord to an overhead beam in a room 240’ high or hang it from a bridge that high or hang it between two buildings. it does not matter. Also, if you hang from a ceiling 240’ high you have a good range of horizontal movement. If you hang from a bridge you could make a really long leap across the river below.

Now, I realize not many homes these days have 240’ high ceilings. You can use a factor of 1/10 stretch and it would still work but 120’ is still a lot. If you are going to jump 12’ you need some overhead space. Let us assume your college gym has ceilings 30’ high and your teachers are willing to play along with the experiment in the interest of science. This is what you can do: You take up the cord to a block (pulley) hanging from the ceiling, then down to another on the floor (or a far away wall) and make the cord go around as many times as needed to take up whatever length you are using. You could also use a rope from your harness, up to a block in the ceiling and out some window where you could have the shock cord made fast to some distant object like a tree.

Then again, if I had 240’ of thick elastic cord I could think of better things to do with it like, say, launching goats a great distance.

10

Here’s the point I was trying to make with the slack line thing - all it amounts to is that the balloon doesn’t stay still while the line goes slack, it begins accelerating upward (albeit slower than the weight) so that when the line goes tight again (as the weight falls back down), the ballon has some energy to transfer to the weight, this may result in a mere reduction of downward velocity or it may (depending on a few factors including height of jump and the ratio of buoyancy to weight) exert enough of a tug to pull the weight upwards briefly.

BTW, I like your bungee cord idea sailor.

11

Mangetout, the point is, as you correctly say, that the balloons will not help you jump higher, which is the whole point of the OP.

12
      • Certainly they would. Mangetout is only pointing out that if you jumped up faster than the balloons could rise and take up the slack, you wouldn’t accomplish much. As the amount of balloon lift got closer and closer to your weight however, its upward force would act faster because it would have more lift in excess of its own weight. You wouldn’t be able to jump up as quickly as normal, because you would always have to move slower vertically upwards than the balloons, but you would be able to jump higher.
        ~
13

:sigh: DougC, you are quite mistaken and totally misunderstanding the physics of the experiment. Neglecting air resistance, a bigger balloon will exert more upward force but will NOT rise faster just like a ton of bricks weigh twice as much as half a ton but they fall at the same rate. Please look at the picture mangetout linked to.

14

Any of y’all looked at the link FearItself gave us?

According to them it both works and is fun.

I wanna try this! INDOORS of course!

15

I don’t want to be a party pooper, but PLEASE be careful:

http://news.bbc.co.uk/1/hi/world/europe/2974342.stm

16

No, I disagree.

I have updated the image I posted above to try to make it a bit clearer:

[LIST=A][li]The system is at rest[/li][li]The weight is lifted, the line goes slack, the balloon begins to accelerate upward[/li][li]The weight is lifted more, the line remains slack, but the balloon is still accelerating upward[/li][li]The weight is released, but is has only just begun to fall, the balloon is still accelerating upward[/li][li]The weight falls a little, and the balloon has accelerated upward some more. because the line is now pulled tight, the energy built up by the upward acceleration of the balloon can now be transferred to the weight[/li][li](assuming that the buoyancy of the balloon is significant in relation to the weight, this extra energy lifts it some more - higher than it would otherwise have gone (the yellow line)[/li][li]The system descends with the line now pulled tight[/li][li]Ditto[/li][li]The system is at rest (ignoring any bounce on the part of any of the elements)[/li][/LIST]

17
      • And you are not reading carefully. I said that you would not be able to jump up faster than the rate of gravity.
  • Consider this example:
  1. A 80 lb person,
  2. A 20 lb empty balloon, and
  3. enough helium to lift 99.99 lbs.
    …
  • Now if the balloon with helium was attached to the person and they crouched down and jumped up slower than the accelleration of gravity, the person, the balloon and the helium will be moving upwards at X speed with 100 lbs of inertia, but the downward force of gravity on the person, balloon and helium will only be .05 lbs. So you would be able to jump up higher, just not any faster than the accelleration of gravity.
    ~
18
19

sailor , what are we missing, look at the link provide by FearItself. How can you look at that and say it doesn’t work? I don’t have time to do the calcs, but I’m with Mangeout

20
      • I have to admit I didn’t lok at the link either the first couple times through – but I had seen it when they had their earlier regular-HTML website. I was looking for it but couldn’t remember the name…
        ~