Harmonic Vibration-Is any data missing here

[jrm2002]

Homework Statement

A structure modeled as a damped spring mass system with mg=2520 lb., k= 89,000 lb/inches,and damping constant c = 112 lb.sec/inches is subjected to a harmonic exciting force.
Determine a)Natural frequency
b)Damping ratio
c)Amplitude of the exciting force when the peak amplitude of of of the vibrating mass is measured to be 0.37 inches.
d)The Amplitude of the exciting force when the amplitude
measured at the peak frequency assumed to be resonant
frequency.

Homework Equations

a)Natural frequency can be determined as the ratio of the square root of stiffness to mass
b)Damping ratio is the ratio of the damping coefficient to critical damping
(2*m*natural frequency)

The Attempt at a Solution

Considering the question (c)

To get, Amplitude of the exciting force when the peak amplitude of the vibrating mass is measured to be 0.37 inches.
Now, amplitude of the vibarating mass is a function of frequency ratio(forcing frequency to natural frequency) as well as the amplitude of the vibrating mass?

So how to obtain the amplitude of the vibrating mass??

Similarly question(d)??

Please , please help!

 

[OlderDan]

This is a rather nice look at the problem

http://www.scar.utoronto.ca/~pat/fun/NEWT1D/PDF/OSCDAMP.PDF