Launch a bottle rocket
How can we explain what happens?
   

 
What is a "Bottle Rocket"?
A "bottle rocket" is a rocket made from a 2 liter soda bottle (shown right). To launch the rocket, pour some water into the bottle. Then the bottle is pressurized using a special latch that keeps the water and air under pressure. When the latch is released, the air pressure pushes the water out, forcing the rocket into the air. If you use the right combination of water and air under pressure, your rocket can travel 60 - 80 m. Bottle rockets should be built and launched with the supervision of a quaified adult.
What happens

Several things happen once the rocket is launched. Move your mouse over the drawing on the right to see them.

  • The air pressure in the rocket pushes the water out
  • As the water leaves the bottle, the air expands and the pressure drops
  • The force of the water pushes the rocekt forward
  • Air drag slows the rocket
Experiments
  1. Find a 2 liter soda bottle and weigh it empty to find the weight of the rocket.
  2. Find the amount of water that makes the rocket go the longest distance. Use the simulator. Set the pressure to 1500 kPa, the mass to 0.2 kg. Set the launch angle to 45 degrees. Be sure to put a check in the "include air resistance box. Try 0.2, 0.5 and 1.5 kg of water. The module draws the path of the rocket when the flight is over. What shape does the flight path take? Why?
  3. How important is air resistance? Use the the mass of water that gave you the longest distance in problem 2 only this time remove the check mark in the "include air resistance" box. How much farther does the rocket travel.
  4. What is the angle that makes the rocket fly the farthest? The answer may suprise you. Use the mass of water that gave you the best distance in problem 2. Try 40, 45 and 50 degrees. Which angle gave the greatest range. What does this tell you about the importance of air resistance?