Pop Bottle Rocket, Part II: Projectile Motion

Objectives

• Explore and demonstrate the effects of balanced/unbalanced forces and action/reaction forces.

• Apply their understanding of forces and their effect on objects to manipulate the flight of toy rockets.

• Use the scientific process (make predictions, conduct a fair test, control variables, gather and interpret data) to manipulate the flight distance of a toy rocket.

Materials

• Per Class:
  a pop bottle rocket launcher -made (See instructions from NASA) or purchased (from an hobby/science supply like Boreal)

  a large field or open area
  a 2L pop bottle
  materials to create fins and nose cones (e.g. scissors, tape, construction paper, foam, foil, cardstock)
  pitchers of water
  safety goggles (for the entire group)
  a protractor
  a stopwatch
  tape measures or metre sticks
  a Launch Angle data sheet
  a pencil

Key Questions

• What is a parabola?
• Which angle did you predict would work best?
• Did your prediction match your experimental res
• Which angle actually worked the best?
• What variables of the experiment did you control?
• Were there any other, uncontrolled variables that might have affected your results (e.g. weather, wind)?

What To Do

Preparation

1. Make or purchase a pop bottle rocket launcher. There are several ways to build a launcher using standard materials from a hardware store. Whichever model you choose, be sure to use pressure rated PVC tubing. Instructions can be found in many online videos, or at: NASA | Water Rockets
2. Build a pop bottle rocket. Add fins and a nose cone to help it fly along a straighter path. Remember that the pop bottle is upside down when it’s launched, so design it with the opening at the bottom. Be careful not to cut into it— any holes or cracks in the bottle will make it impossible to pressurize.
   

Activity

1. Choose 5 different launch angles between 0–90° to test. (90° = straight up, and 0° = horizontal). Make a prediction relating the launch angle to distance travelled end.
2. Head to the launcher and pour 300–400mL of water into the rocket.
3. Lift the handle on the launch pad and carefully fit the pop bottle onto the nozzle. Ensure that the bottle is locked in.
4. Find four volunteers to be the “launcher”, the “pumper”, the “timer”, and the “measurer”. The launcher and pumper put on safety goggles, the timer receives a stopwatch, and the measurer, the metre sticks.
5. The “pumper” adds 5 big pumps of air into the pop bottle. Be sure not to go past about 40 psi (5–6 bike pumps) as greater pressure can rupture the bottle rocket.
6. The “launcher” moves the rocket to the desired angle using the protractor, counts down, and launches the rocket.
7. The “timer” times the length of the flight from launch to landing and the “measurer” measures the range of the rocket and records it on the data sheet.
8. Repeat for each of the angles, pumping the launcher to the same psi. Record all of the time and distance results.
9. Discuss the results.

Extensions

• Work in small groups to design, build, and test your own rocket. (Hint: Have a few launchers available so groups can test many angles.)
• Follow up with the activity Pop Bottle Rocket, Part III: Mass and Force. Experiment with the amount of water you add. What happens if you half-fill the bottle with water? How far can you get a bottle to go?
• After doing both Part II and Part III, combine your discoveries to come up with an experiment that tests the best combination of launch angle and rocket mass.

Other Resources

Science World Resources | Pop Bottle Rockets I: Action and Reaction

Science World Resources | Pop Bottle Rockets III: Force and Motion

NASA | All About Water Rockets