Resonance frequency and Natural frequency?

In summary, Resonance frequency and Natural frequency are two different things. Resonance frequency is the frequency of the undamped form of the oscillator, while resonance frequency is the frequency of the oscillator when it is driven. The difference between the two is that resonance frequency is the frequency of the oscillator when it is driven, while resonance frequency is the frequency of the oscillator when it is excited.
  • #1
tksxkdhkd11
4
0
Resonance frequency and Natural frequency??

Say there is an empty bottle of coke., and you know for sure that
the bottle resonates most at 320hz.
when the bottle resonates, the bottle will vibrate.
the question is,
1.if the bottle also resoates at 318hz( bu not most), will the bottle vibrate 318 times per second or 320times per second.?

2.What is the difference between resonance frequency and resonance frequency?? Aren't they basically the same??
 
Physics news on Phys.org
  • #2


tksxkdhkd11 said:
Say there is an empty bottle of coke., and you know for sure that the bottle resonates most at 320hz.
when the bottle resonates, the bottle will vibrate.
the question is,
1.if the bottle also resonates at 318hz( but not most), will the bottle vibrate 318 times per second or 320times per second.?
As I read it from http://en.wikipedia.org/wiki/Harmonic_oscillator#Sinusoidal_driving_force, it will resonate at the driving frequency.
2.What is the difference between resonance frequency and resonance frequency?? Aren't they basically the same??
I assume that's not what you meant to ask.
 
  • #3


Welcome to PF;
A simple harmonic oscillator resonates at the natural frequency of the undamped form of the oscillator.

http://en.wikipedia.org/wiki/Harmonic_oscillator#Driven_harmonic_oscillators

However, the phenomenon of resonance is not restricted to simple harmonic oscillators.
http://en.wikipedia.org/wiki/Resonance

To your questions:
if you drive an oscillator - it will vibrate at the driving frequency.
if the driving frequency is not the resonant frequency, then the amplitude of the oscillations will be lower.
(See first link above "sinusoidal driving force".) The exact details depend on how the oscillator is driven.

Some systems will have more than one resonant frequency - i.e. a length of string can resonate in a series of modes though only the fundamental would be thought of as the "natural" frequency of the string.
 
Last edited:
  • #4


I don't find the term 'resonance frequency' very helpful. I prefer 'natural frequency'; it is the frequency of the body's free oscillations, so it is defined independently of forced oscillations. The phenomenon of resonance is that forced oscillations have maximum amplitude when the applied forcing frequency is at (or very near) the body's natural frequency. When the body has more than one natural frequency, I'd expect peaks of amplitude when the forcing frequency is equal to any of these frequencies.
 
  • #5


I don't find the term 'resonance frequency' very helpful
because you tend to confuse the phenomenon, "resonance" with the property "resonant"? I can see where thet would be a pain. Unfortunately,
the body's natural frequency
... has been goniffed by the pseudoscience, alt-medicine, crystal healing, etc. crowd. I live on an island retreat for such people so I cannot use that term without trouble ;)
 
  • #6


My unease about "resonance frequency" is that students who use the term know that this is the frequency of applied force at which a body's oscillations have maximum amplitude, but they don't always know that this frequency is that of the body's free (unforced) oscillations (or close to it).
 
  • #7


An ideal resonator will just not respond to any other than its natural frequency of oscillation. If you excite it with an impulse, then it will oscillate at its natural frequency. A real resonator always has losses (it's an RLC circuit and not just an LC circuit equivalent). It has a resonance response to other frequencies - a narrow or wide bell shaped curve of frequency against amplitude of oscillation. The width of the curve depends upon the Q Factor (1/Q, actually). If you excite it at a frequency near its natural frequency it will not suddenly change frequency but oscillations will carry on at the excitation frequency and the amplitude will decay. (A real resonator will oscillate at its natural frequency when given an impulse.)
 

1. What is the difference between resonance frequency and natural frequency?

Resonance frequency is the frequency at which an object or system vibrates with the greatest amplitude when subjected to a periodic force. Natural frequency, on the other hand, is the frequency at which an object or system vibrates without any external force applied, based on its physical characteristics such as mass and stiffness.

2. How is resonance frequency calculated?

Resonance frequency can be calculated using the formula f = 1/2π√(k/m), where f is the resonance frequency, k is the spring constant, and m is the mass of the object or system.

3. What factors affect the natural frequency of an object or system?

The natural frequency of an object or system is affected by its mass, stiffness, and damping. Increasing the mass or stiffness will increase the natural frequency, while increasing damping will decrease the natural frequency.

4. Why is resonance frequency important?

Resonance frequency is important because it can cause significant vibrations and even damage to objects or systems if it matches the frequency of an external force. It is also used in various applications such as musical instruments and tuning circuits.

5. How can resonance frequency be controlled or avoided?

Resonance frequency can be controlled or avoided by adjusting the mass, stiffness, or damping of an object or system. In some cases, adding dampers or changing the shape or material of the object can also help to change the resonance frequency. Additionally, careful design and engineering can help to prevent resonance from occurring in critical systems.

Similar threads

Replies
2
Views
900
Replies
2
Views
2K
Replies
2
Views
898
  • Electromagnetism
Replies
27
Views
3K
  • Introductory Physics Homework Help
Replies
17
Views
223
  • Electromagnetism
Replies
4
Views
1K
Replies
1
Views
1K
  • Other Physics Topics
Replies
12
Views
3K
  • Electromagnetism
Replies
3
Views
1K
  • Electromagnetism
Replies
4
Views
2K
Back
Top