if they are HL2 models then in the model browser it will say that next to their name it will say HL2 or TF
Simply try them all out as dynamic to see if they need to be, you can also look in the model browser window, click the info tab (might not be info, its the one on the end) and it should have some tickboxes, static dynamic and physics: those that are ticked it can be. however, this isnt 100% accurate