the bottle.
use tape to secure the straw to the bottle.
blow through the straw to inflate the balloon, then put your finger over the tip of the straw to trap the air. what do you think will happen when you put the car down and release your finger?
put the car down on a flat surface and release your finger. what happens?
see what adjustments you can make to make the car go farther.
what happens if you inflate the balloon more?
what happens if you adjust the direction the straw is aimed? does it work best if the straw is aimed straight back?
extra: there are many different ways to build a balloon car. turn 