Intro

Worksheet

Activity: Controlled Propulsion Experiment - Film Canister

A film canister, Alka Seltzer, and water can demonstrate how a rocket engine works. The Alka Seltzer in the film canister, when mixed with water, produces a gas. When there is too much gas to hold in the canister, we say there is a high amount of pressure. This pressure needs to be released, so the lid of the film canister pops off.

You are going to demonstrate this and measure the distance the canister travels. Your mission, should you choose to accept it, is to model the thrust that is produced in a rocket.

Materials:

• film canister (generic film type--Kodak lids are too tight.)
• drinking straw
• scissors
• string (5-8 meters long)
• tape
• worksheet
• graduated cylinder
• water
• quarters
• safety glasses

Procedure:

1. Cut a piece of drinking straw so that it is a little shorter than the length of the film canister.
2. Tape the piece of straw to the film canister so the straw is parallel to the canister. (Make sure you leave enough room for the lid!)
3. Slide the string through the hole of the straw so that the lid of the canister is facing the opposite direction of the string's path.
4. Choose two people to hold the ends of the string taut and level. Everyone MUST put on safety glasses before continuing to Step 5!
5. Put one-quarter tablet of Alka Seltzer and 2 mL water into the film canister and quickly close the lid. The person holding this end of the string should hold it to the side. NO ONE should stand behind the canister.
6. After a short period of time, the lid will pop and send the canister down the string. Measure the distance traveled and record your results on the chart shown below.
7. Tape one quarter on the end of the canister and repeat the experiment. Record your results.
8. Tape two quarters on the end of the canister and repeat the experiment. Record your results.

Number of Quarters	Distance Traveled
0
1
2

9. How is the Propulsion Pop! Activity similar to a rocket? How is it different? Click Rocket Propulsion to access information on rockets from the Beginner's Guide to Propulsion.

10. What happened when you added one quarter? Two quarters?

11. Why do you think your results turned out the way they did?

12. If you could modify this experiment, what would you do differently? Be detailed in your explanation.