Science activity
Pendulum Patterns
Swing things back and forth! Tie a toy to a string and watch it swing like a clock. Count the swings together and see the pattern — it keeps going the same way!
Materials and setup
- string
- washers or small weights
- tape
- ruler
- stopwatch or timer
- paper
- pencil
- paint (optional for pendulum art)
How this changes by age
Pre-K (ages 3–4)
Swing things back and forth! Tie a toy to a string and watch it swing like a clock. Count the swings together and see the pattern — it keeps going the same way!
Steps
- Tie a small weighted object (washer, toy) to a string about 1 foot long.
- Hold the top of the string and let the weight swing back and forth.
- Count the swings together: 'One, two, three... It keeps swinging back and forth in a pattern!'
- Try pushing it gently vs. hard. 'Does it swing faster or just go higher?'
- Make a pendulum painting: dip the weight in paint, swing it over paper, and watch the beautiful pattern it makes.
- Tell a grown-up one thing that surprised you.
Learning objectives
- Observe that a pendulum swings in a regular, repeating pattern
- Count pendulum swings to practice rhythmic counting
- Notice that pushing harder makes the swing bigger but not faster
Kindergarten (ages 5–6)
Build pendulums of different lengths and discover that longer pendulums swing slower. Count and compare swings to find the pattern.
Steps
- Build 3 pendulums with different string lengths: short (6 inches), medium (12 inches), and long (24 inches). Use the same weight on each.
- Swing the short pendulum and count how many swings it makes in 15 seconds. Record the number.
- Do the same for the medium and long pendulums.
- Compare: 'Which one swung the most times? Which was slowest?'
- Make a prediction: 'If we made an even LONGER pendulum, would it swing more or fewer times?'
- Draw your three pendulums and write the number of swings next to each.
- Tell a grown-up one thing that surprised you.
Learning objectives
- Discover that pendulum length affects the speed of swinging
- Count and compare swing data across different pendulums
- Make predictions based on observed patterns
Early elementary (ages 6–8)
Investigate pendulum physics systematically: test how length, weight, and release angle affect the period. Collect data, create graphs, and discover Galileo's pendulum law.
Steps
- Build a pendulum: tie a weight to a string, hang from a doorframe or shelf edge using tape.
- Test LENGTH: keep weight and release angle the same. Time 10 full swings for string lengths of 10cm, 20cm, 40cm, and 80cm. Calculate the period (time for 1 swing).
- Test WEIGHT: keep length and angle the same. Try different weights (1 washer, 3 washers, 5 washers). Time 10 swings for each. Does weight matter?
- Test RELEASE ANGLE: keep length and weight the same. Release from a small angle, medium angle, and large angle. Time 10 swings for each. Does angle matter?
- Create a data table and bar graph for each variable. Which variable affected the period? (Spoiler: only length matters!)
- Research: Galileo discovered this in the 1600s by watching a chandelier swing in church. Write about his discovery and how pendulums are used in clocks.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Design controlled experiments testing one variable at a time
- Discover that only length affects a pendulum's period
- Collect timing data and create graphs to display results
Upper elementary (ages 8–10)
Conduct a rigorous pendulum investigation: derive the mathematical relationship between length and period, explore coupled pendulums and resonance, and connect to real-world applications.
Steps
- Test at least 8 different pendulum lengths (5cm to 100cm). For each, time 20 full swings and calculate the period. Record in a data table.
- Graph period vs. length. Notice the curve is not straight. Now graph period vs. square root of length. Is THIS graph straighter? This reveals the mathematical relationship: T = 2pi * sqrt(L/g).
- Calculate the theoretical period for each length using the formula (g = 9.8 m/s2). Compare your measured values to the calculated values. How close are they?
- Build coupled pendulums: hang two pendulums of the same length from the same horizontal string. Start one swinging and watch. Energy transfers to the other one! This is resonance.
- Research pendulum applications: grandfather clocks, Foucault pendulum (proves Earth rotates), seismographs, metronomes. Explain how each uses pendulum properties.
- Write a physics paper: present your data, graph analysis, mathematical relationship, coupled pendulum observations, and real-world applications. Discuss sources of experimental error.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Derive the mathematical relationship between pendulum length and period through data analysis
- Demonstrate energy transfer between coupled pendulums through resonance
- Apply the pendulum formula to predict periods and evaluate experimental accuracy
Safety and evidence note
Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.
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