This article is from the Star Trek Tech FAQ, by Joshua Bell inexorabletash@hotmail.com with numerous contributions by others.
In "Encounter at Farpoint" [TNG], Data threw a Holodeck-generated rock
at the wall. There are a few possibilities. Either the computer
realized the intent of the demonstration, and didn't replace the rock
with an image on the Holodeck wall; or the "simple pattern" of that
simulation didn't allow for treadmill-scrolling; or the Holodeck
computer wasn't quite powerful enough, pre-Bynar intervention.
In "Ship In A Bottle" [TNG], Data throws his own communicator at the
wall. The Holodeck must have safeguards not to summarily destroy
things it didn't create, so it didn't do anything to affect the
communicator.
 
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