How can a rocket balloon fly?

We made a rocket balloon using a balloon, a straw and some string.

Predictions:  Will it fly?   Yes - 17,  No -1

Prepare for blast off......

Wonderings and Questions:

•  "What would happen if we blew it up bigger?"  - Rithush

  We tried it out and the balloon went further.

• "What if we point the balloon the other way?"  - Gabby

    We tried it out and saw that the balloon went the opposite way.

• "I wonder if we could fold the balloon up?"  - Ezekiel

     It went really slow. The air couldn't get out very fast.

• "How about we tie up the balloon and put a wee hole?" - Ody

     Would it go faster or POP?   It POPPED!

The air coming out of the balloon pushes the rocket the opposite way.