The Balloon Rocket Experiment

The balloon rocket experiment is a great way for kids to investigate the uses of pressure while having a lot of fun in the process. The materials required are extremely low cost, there is no danger involved and the experiment can provide your child with much entertainment. For older children, the experiment can also be used to perform calculations of velocity which can be graphed.

Materials Needed: You will need the following:

* a balloon
* some cotton thread
* a straw
* sticky tape

Optional materials for extension of the experiment:

* a tape measure
* a stopwatch

Procedure:

Push the cotton through the straw then stretch the thread across a room. The thread needs to be taut, so it is best to secure the ends to fixed objects. Next, blow up the balloon without tying up the end of it and tape the balloon to the straw as shown in the diagram. Once the balloon is secured to the straw, release the end of the balloon. It will then go flying along the cotton thread across the room.

What is Happening?

This balloon rocket experiment uses the pressure difference between the gas inside the balloon to that outside the balloon. The gas inside moves towards the area of lower pressure. The gas pressures are moving towards an equal state; technically this is called moving toward equilibrium.

This experiment is a good demonstration of the ability of pressurized air to make an object move.

Extending the Experiment

This experiment can be extended by measuring the distance the balloon travels in metres and dividing it by the time taken in seconds. This gives the average velocity of the balloon over the course of the journey in metres per second, which is an excellent hands on way to introduce or reinforce this topic. It may take several trials to get an accurate recording of the time taken.

Further Extension

The more trials that are run, the more stretched the balloon becomes. If the balloon is inflated to a constant size, the result will be a gradual decrease in the velocity of the balloon due to the walls becoming stretched. This lends itself to recording the velocities of the balloon over a series of trials; at least 10 trials should be run to get a good data set.

The results of velocity against trial number can then be graphed either by hand or with spreadsheet or graphing software such as Excel. This can then be even further extended to equation generation using CAS software or the like.