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Shake three toys on springs gently. Why does only one go wild?
Resonance lab · Last updated: 16 October 2026
Three toys hang on springs from the same bar. You shake the bar gently at a steady rate. Two toys barely move, but one starts swinging further and further. The lab shows why matching rhythms build up big motions.
What you'll discover
- Every springy object has its own natural rhythm of vibration.
- Small pushes timed to match that rhythm build up very large swings: this is resonance.
- Pushes at the wrong rhythm mostly cancel out and produce little motion.
The science in plain words
Anything that can vibrate, such as a toy on a spring, a swing or a guitar string, has a natural frequency: the rate at which it bobs or swings when left alone. That frequency depends on things like its mass and how stiff its spring is.
If you push it at random times, some pushes help and some fight the motion, so it never gets going. But if you push in step with its natural rhythm, every push adds energy at just the right moment. The swings grow bigger and bigger. This is resonance. A child on a playground swing uses it without thinking, pumping their legs in time with the swing.
In the lab, the three toys have different natural frequencies. Shaking at one rate matches only one of them, so only that one goes wild. Change the rate, and a different toy takes its turn.
Resonance is useful in musical instruments, radios that tune to one station and microwave ovens. It can also be dangerous: engineers design bridges and buildings so that wind, footsteps or earthquakes do not shake them at their natural frequency.
Where it fits
- India, NCERT: Resonance goes beyond the NCERT syllabus for classes 6 to 10; it builds on vibration and frequency in Class 9 Chapter 11: Sound.
- United States: Grades 6 to 12
Common questions
What is resonance in simple words?
Resonance is when small, regular pushes build up a big vibration because they match the object's natural rhythm. Pushing a swing at just the right moment each time is a good example.
Can resonance break things?
Yes. If a structure is shaken at its natural frequency for long enough, the vibrations can grow until something cracks. That is why engineers design bridges and buildings to avoid it.
What decides an object's natural frequency?
Mainly its mass and its stiffness. A heavier toy on a spring vibrates more slowly, and a stiffer spring makes it vibrate faster.
Related labs
- Bungee Toy: Hang a toy on a big spring and let go. Does a heavier toy bounce faster or slower?
- Standing Waves: Buzz a cord at just the right rate and it splits into still points and big loops.
- Simple Pendulum: Time one swing. What changes it: the string, the bob, or the push?
See all physics labs or every Taz science lab.
Try it yourself
The Resonance lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.