Friction Books Experiment

Last week our class conducted an experiment where we wanted to know which materials increased friction and decreased friction.  First, we pushed a heavy book only on a cardboard and recorded our observations.  Second, we pushed the heavy book on the cardboard over some pencils and recorded our observations.  Lastly, we pushed the heavy book on the cardboard over some marbles and again, recorded our observations. 

We concluded that the marbles had the reduced friction because they are round and smooth and rolled easily on the carpet.  The cardboard alone had the most (increased) friction because the cardboard did not slide easily when pushed.