11-7 Friction as Centripetal Force, Present Lab Data

HMWK:  p. 123, #19-24,27.  Due Wednesday. 
Today in class: Discussed how friction can act as a Centripetal (center-seeking) force if it is what keeps an object move in a curved path, such as a car moving around a corner, or you turning a corner in the hall:  if there's not enough friction, you can't accelerate (you maintain the same speed and direction) which usually means bad things if you have some velocity that you were intending to change. 
We also went over the work to answer questions from Friday that were on the board, and then allowed each group to present from their friction experiment: IV, Hypothesis, How it was tested, Observations, and Results to the class.  Some of the more interesting findings were the effects of water on friction; in most of the tested situations, water actually increased frictional force.   Some hypothesized that this was the result of a "suction cup" effect - probably the result of interesting chemistry surrounding water.
Be sure to see Friday's post for the new OPTIONAL ASSIGNMENT