# Homework Help: Resonance-The frequency of an applied force

1. Apr 21, 2014

### Woolyabyss

This isn't so much homework as it is me having trouble understanding a concept.
I'm having trouble understanding resonance the definition in my book is

"If the frequency of a periodic force applied to a body is the same as or very near to its natural frequency that body will vibrate with very large amplitude. This phenomenon is called resonance."

I don't understand how a force can have a frequency when its not material.Would it not need to vibrate to have a frequency?
Any help would be appreciated

2. Apr 21, 2014

### electricspit

When an object is set into any oscillatory motion it has a frequency, let's say for simplicity, that it 'prefers' to oscillate at. This is its natural frequency. It doesn't have to be in motion to have a natural frequency, but once it is set into non-forced oscillatory motion it will oscillate at its "natural frequency".

Does this clear things up?

Think of a mass-spring system horizontally, if you perturb the system and set it in motion, it will oscillate at its natural frequency after any transients have left the system.

3. Apr 21, 2014

### Woolyabyss

Ya thanks,
I read the definition a bit more closely and realized they weren't saying that the actual force itself had frequency