Rocket balloon in a parrallel line

Our teacher just gave us a priject to complete and i cannot figure it out. first of all we have limited supplies. we can use 5 ballons, 6 straws, 10 paperclips, 5 rubberbands, a whole roll of masking tape, scissors and a guide wire that cannot be altered. Our goal is to get the a balloon to go across the room one way and back. Our limitations are we can only use the supllies given to us, we cannot intervene with the contraption after setting it up, and the guide wire cannot be altered from its position, which is parrallel to the floor. i have already gooten acroos one way but i can't find a way to bring it back. My teacher hinted it had somthing tod o with gravity, but i can't figured it out. i've spent a couple hours dor two days on this and can't come up with the solution. I have to turn in my design by tommorow AND i have to show that my experiment works, i only get 2 trails. Any ideas PLEASE


Homework Helper
When you say "the guide wire cannot be altered", I'm not sure what that means. Is it just that you can't bend the wire? Is it already fixed in place, or can you reorient it?
I can untie it, to pun a straw through it but then i have to tie back up parrallel to the ground. I cant have it in another orientation


Homework Helper
"Something to do with gravity...". What are you studying in class that this project is intended to support?
We are studyig about Newtons laws, so i thought i was supposed to use air pressure to propell the balloons across, but my teacher just said to think out of the box and use gravity


Homework Helper
I'm sorry, honey, but I'm drawing a blank here. Everything that I've thought of has been eliminated by the stated conditions. All I can think of at the moment is to set up the scissors so that one of the balloons is popped when the "contraption" reaches the end of the first leg, but I doubt the reaction would be enough to propel it all the way back across the room.

The only other comment I can make is that I'm suspicious about that "whole roll of masking tape" thing. That seems excessive, and I'm wondering if he has something in mind using that.

I will keep thinking about it, though, but don't hold your breath.

Edit: Wait a minute. Could you set up the rubber bands to act as slingshots? Don't inflate the balloons, but use the rubber bands on one side to propel the contraption across and set some up on the other side so the contraption bounces off of them? Well, that's a better idea than the scissors one, anyway.
Last edited:
hey does anyone in this post have AIM, cause i need some help with physics problems! if anyone of you do email me at!
Thank You very much for your help, i really do appreciate it:smile:
I can only think of a dubious way that doesn't use gravity.

If you cut two rubber bands into strips and stretch them over the top and bottom of a timer balloon <O>, then when the ballooon runs out of air, the bands won't be pulling so strongly. So if you have two side balloons o<O>o, and attach the bands to a vertical paperclip that presses the neck of the balloons to a straw, you might be able to get a timer thing happening.

It's uh, a bit dodgy.


Staff Emeritus
Science Advisor
Gold Member
Could you use the sissors as a weight around the rope, such that when the "go" balloon deflates, the sissors attached to it fall down with the balloon (gravity :-) and pull off the paperclip that is holding the nozzle of the "driving-back" balloon ?

Just a wild guess...
across the room, that could mean any direction right? on the Y axis or Z axis :-)


I don't see how gravity applies if the wire is parallel to the ground, so if you need that, I can't help. But....

What I'd do is try to use one balloon and a rubber band to hold another balloon (facing the opposite direction) closed. The first balloon would have the rubber band around it and also around the nozzle of the second. As the first balloon deflates, the rubber band around the nozzle of the second loostens and the second balloon propells the rig back across the room.

Tom Mattson

Staff Emeritus
Science Advisor
Gold Member

How did you get the balloon to make the 1-way trip? Knowing that might help people figure out how to get it back.

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving