What is dominant frequency and how to determine it?

[Anonymous]

Hi all,
I have a 2 body system, images attached. they both form an assembly for an transient response analysis.
since i am going to do transient response, solver requires that i feed the following in autodesk nastran.
Damping value (%), Dominant Frequency ( W3) and Dominant frequency( W4). 
I read the pages on the above terms as well as ball non linear transient exercise. 
I have run the modal analysis twice of both parts excluding other each time.
i got some frequency response for both parts ( how do i decide which one is dominant frequency). One tutorial states that the first mode is dominant & natural frequency of the body and i have to take the highest mode frequency out of both parts as dominant frequency of the assembly system , is that right? 
I have attached model results in images, could you help me decide please?

[Roelof.Feijen]

Hello @Anonymous ,

To determine the dominant frequency constrain (fully fixed) the area of the model that you expect to make contact with the ground (or other impactor) and run a normal modes solution with ~20 modes. Look at the mode shapes and find the mode you would consider to be the “dominate” response of the structure during/after impact. A look at the modal effective mass table in the *.OUT file may also help determine the critical mode.