Cosmo plucks the low string of a guitar, softly first, then hard. The hard pluck is louder, but both notes sound the same.
The string seems to have a built-in vibration rate of its own. This lesson names that rate.
Earlier in the course, you met frequency: the number of complete repeats each second, measured in hertz, first counted for spinning objects.
An oscillating system has a frequency the same way: the number of complete back-and-forth swings each second.
Pluck the guitar string gently, and it vibrates at one particular frequency.
Pluck the same string hard, and the swings are bigger, but the string still vibrates at that same frequency.
The disturbance chooses how big the oscillation starts. The system itself chooses the frequency.
A different system has its own, different natural frequency. A short stiff ruler clamped to a desk vibrates faster than a long floppy one.
Natural frequency pays off twice later in this course: it decides which patterns a vibrating string settles into, and what happens when something is nudged in time with its own rhythm.
Dilys flicks a ruler clamped to a desk, first gently, then much harder. How do the two vibration frequencies compare?
A disturbed system left alone oscillates at its natural frequency.
The flick strength changes how big the swings are, not the system.
The two frequencies are the same: the ruler vibrates at its own natural frequency both times.
A bobblehead dog nods after a tap. Anselm taps it again tomorrow. What sets the frequency of its nodding each time?
Once tapped and left alone, the system oscillates at its natural frequency.
The bobblehead is the same system both days.
The bobblehead's own natural frequency sets the nodding rate, the same frequency both days.
Beata flicks a mounted door stopper spring gently, and later flicks the same stopper much harder. How does the frequency of its vibration compare across the two flicks?
Cosmo flicks a short stiff car antenna, then flicks a longer, floppier antenna on another car. How do the two vibration frequencies compare?
A gust shakes a stop-sign pole and dies away. Beata says: 'The pole now sways at the pole's own natural frequency, not at a frequency the gust chose.' Is Beata correct?
A flicked car antenna vibrates and slowly settles. Which statement about the frequency of its vibration is correct?
Which change gives a vibrating system a different natural frequency?
The one particular frequency at which a disturbed system, left alone, always oscillates is called its ___.