Compound Harmonic Lissajous Sand Pendulum
A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.
Materials Needed
- • Small plastic kitchen funnel (1 unit)
- • Fine dry sand (colored decorative or play sand) (2 cups)
- • Smooth nylon string (4 meters)
- • Large black poster board (1 sheet)
- • Tension bar or doorway frame mounting hooks (1 set)
Pro Tips
- → Suspend the funnel from a Y-shaped double-string harness: one axis swings along the upper string, while the cross axis swings from the lower knot.
- → This setup creates two different pendulum lengths on perpendicular axes, producing distinct frequency ratios like 1:1, 1:2, or 2:3.
- → Plug the funnel tip with a finger, release it in an elliptical swing over dark paper, and watch Lissajous curves trace out in sand.
Safety First
Place a drop cloth or wide tray underneath the pendulum to collect pouring sand.
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Step-by-Step Instructions
Step 1
Rig a Y-shaped string harness from two points on a doorway frame, joining the cords at a sliding central knot.
Step 2
Suspend a small plastic funnel from the central knot with a short cord so the tip sits 2 cm above the floor.
Step 3
Lay a sheet of black poster board flat underneath the funnel and fill the funnel with dry, fine colored sand while plugging the tip.
Step 4
Pull the funnel back diagonally and release with a gentle sideways push, watching escaping sand trace complex geometric Lissajous curves.