# How do you find the force extended if given the amplitude? Forced Oscillations

1. Nov 27, 2012

### randoreds

How do you find the force extended if given the amplitude? Is main questions, I also have one slight question.

Ok, doing a problem. There is no damping. A (.15kg) object is hanging from a light(6.30N/m) spring.

A sinusoidal force with an amp of 1.7 N drives the system. And the problem is asking at what frequency will the force make the object vibrate with an amp of .44m

So I'm solving and my final equation is ω^2= w°^2 plus or minus (( Fext/m)/A)
Where ω = natural frequency and ω°= frequency of the driving force.

So my questions are how would I find the force extended given the amplitude and ω^2= w°^2 plus or minus (( Fext/m)/A(------ Would I plug in .44 for that A?

2. Nov 28, 2012

### Simon Bridge

What does "force extended" mean?
What role does it play in the motion?

Is the situation one that is transient or steady-state?
Do you have equations for those situations in your notes?

note: $F_{ext}$ is usually notation for an external force... just saying.

Last edited: Nov 28, 2012
3. Nov 28, 2012

### randoreds

Thanks, I can't believe I didn't think of that! I got the right answer.That took way longer than it should have!

4. Nov 28, 2012

### Simon Bridge

Very often in science, it is not so much a question of getting the right answers as asking the right questions :)