demonstrations:the_spinning_can
The Spinning Can
Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★★☆ Can be done by science teachers
Safety: ★☆☆ Minimal safety procedures required
Categories: Energy, Force, Motion
Alternative titles: Newton’s Laws Water Can Demo
Summary
A can with small angled holes near its base will spin when filled with water and suspended.
Procedure
- Take an empty soda can with its pull-tab intact (or a soup can).
- Use a nail or ice pick to make four small, equally spaced holes around the bottom rim.
- As you punch each hole, push the tool sideways so each hole is slanted in the same direction.
- Bend the can’s pull-tab upward and tie fishing line to it. For a soup can, punch two holes near the top rim and run string through them.
- Submerge the can in water until it is completely full.
- Lift the can using the string over a bucket or tub.
- Watch as water streams out of the slanted holes, causing the can to spin.
Links
Spinning Soda Can Experiment (Newton's Laws of Motion) - Kids Fun Science:
📄 The Spinning Can - cmste.uregina.ca: https://www.cmste.uregina.ca/Quickstarts/spinningcan.html
Variations
- Try different numbers of holes (2, 3, 4, or more) to see how it affects spinning speed.
- Vary hole sizes to compare how water flow rate changes the can’s motion.
- Test different can sizes (small soda can vs. large soup can).
- Add a fishing swivel to the string above the can for smoother rotation.
Safety Precautions
- Use caution when punching holes to avoid slipping and cutting yourself.
- Keep the workspace dry to prevent slipping hazards from spilled water.
- Supervise younger students when handling sharp tools.
Questions to Consider
- Which of Newton’s laws explains why the can starts to spin? (Newton’s Third Law: the water pushes one way, the can reacts by spinning the opposite way.)
- How does the number of holes affect the spinning speed? (More holes increase force, but also drain water faster, affecting rotation time.)
- Why must the holes be slanted instead of straight? (The angled jets produce sideways thrust to create torque; straight jets would just flow downward.)
- How does this experiment relate to real-world applications? (It demonstrates principles similar to jet propulsion, rockets, and turbines.)