There's a big lack of physics objects around to pick up and throw on the first map.
But there is one physics-affected wrench available near where the scientist with the clipboard beckons you over a second time.
Poking/throwing the wrench at any of the scientists elicits no response, but doing this to the guards ellicits the Postal Freeman lines, telling Freeman to stand down rather aggressively and trying to call for the Emergency Response Team.