- At least two prepared leader
- 1 balloon per group (have different shapes for them to choose from)
- 1 piece of string at least 10 feet (3 meters) long
- 1 drinking straw
- masking tape
- yardsticks or measuring tapes
- *handout to record information
- stopwatch (optional)
- paper clips (optional)
- Newton's third law of motion
- Working in a small group
- Scientific method review (hypothesis, project design, data collection, conclusions)
- Observation and data recording
- Understanding of Newton's third law
Space rockets need a lot of force to be propelled into outer space. What makes the rocket move? The following activity illustrates Newton's theory that "for every action there is an equal and opposite reaction." In this case the "action" of the gases escaping the balloon will cause the "reaction" of the rocket moving forward.
Description of activity:
* Estimated prep time (before student arrival): 45min-60min
* Estimated activity time 60min or more (depending on number of trials)
1) This activity can be set up as a contest to get kids more excited! Give each group all of the materials, but let them come up with their own design.
2) Step one: Hypothesis: Guess what will make a balloon go farther. Talk about aerodynamics, friction, and (optional) inertia, potential energy and kinetic energy.
3) Step two: Design an experiment: Discuss error, and have them come up with ideas of where error in an experiment would come from. Write these ideas up on the board. Then, talk about how they can reduce their error in an experiment. (If there is one person timing and one person releasing, the person releasing should count to three before they let go. Put a mark on the string where the balloon starts so you can measure from the same place every time. Make sure the string is taut before every trial! etc.)
4) Design the experiment and predict how far the balloon will travel, and what the "flight" pattern will look like. Are there ways to stabilize this path? Would that make it go farther?
5) Break up into small teams (3-5 students) and create the apparatus.
6) Feed string through straw. Attach string to walls or chairs. Blow up balloon and twist off the end (DON'T TIE THE END). Tape to straw. Hold until it's time to release. (See picture on handout)
7) Perform the experiment. Record all times, distances, flight patterns, or other interesting observations.
8) Regroup and see who won!
Review and Questions:
The experiment showed that shapes of balloons (aerodynamics), amount of air in balloon (amount of force), and other variables (paper clips for weight, taut string!) effect the flight of the rocket. The same ideas go into designing real rockets!
1) Ask what worked the best? Why?
2) Ask kids what moved the balloon forward.
3) Discuss what this experiment has to do with Newton's third law. (i.e. the force of the air out of the balloon pushes on the air which pushes back on the balloon)
- Rocket handout: http://www.teachercreated.com/pdfs/lessons/010216is.pdf
Alternatives for older/younger ages:
- For older students you can talk about kinetic vs. potential energy. The balloon has PE when it's full and KE when it's released. Also, expand the experiment to vary thrust (more balloons) and load (add paperclips to the straw for weights). Try different balloon sizes and shapes and record differences.
- Not recommended for younger students