Lesson 8 of 8 · Waves
Resonance and Natural Frequency
🌊
🎯 Your mission
Predict it first. Then prove yourself right (or wrong).
⚡ The twist
Nature loves to surprise the careful watcher.
What you'll learn
Every object has a natural frequency at which it vibrates most readily. Drive it at exactly that frequency and each push arrives in step with the motion already there, so energy accumulates and the amplitude grows far beyond what the same force produces at any other frequency. That is why a held note can shatter a wine glass, why a radio tuner picks out one station from thousands, and why bridge designers deliberately place the structure's natural frequencies away from the rhythm of walking feet.
Key words
natural frequency
The frequency at which an object vibrates most readily when disturbed and left alone.
resonance
The large build-up of amplitude that happens when a driving force matches an object's natural frequency.
Make a hypothesis first
Before you start: write down what you think will happen, and why.
Say your guess out loud — then find out if you were right.
Get ready
🧰 What you need
- string
- three masses
- clamp stands
- stopwatch
- ruler
Get ready
⚠️ Safety first
- Clamp the stands to the bench so they cannot topple, and keep the swinging masses clear of faces.
Step 1 of 4 · Read
Think about what you just learned: say what "natural frequency" and "resonance" mean in your own words before you start.
Step 2 of 4 · Do
Hang three pendulums of different lengths from one loose horizontal string. Drive the string gently at the natural frequency of the middle pendulum and record which of the three builds a large amplitude and which barely move.
Step 3 of 4 · Observe
Record what actually happened, including anything that did not match what you expected.
Step 4 of 4 · Record
Write a conclusion that answers the question this lesson opened with, and state your uncertainty.
Question 1 of 3
Question 2 of 3
Question 3 of 3
Mind = blown
🔬 The more you look, the more nature shows you.
Nice work!
You got 0 of 3 right.
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✨ More to explore
🌍 Where you see this in real life: This shows up in your everyday life more than you'd think.
🏆 Stretch challenge (try it this week): Try one experiment in real life this week — even a tiny one.
👨👩👧 For the dinner table: “What's the most surprising thing you learned today?”
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Ready?
Resonance and Natural Frequency
Predict it first. Then prove yourself right (or wrong).
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Print the whole Waves track
All 8th Grade Waves lessons as a printable PDF, with worksheets and answer keys.