  When a ball hits a surface, does the angle of reflection always equal the
angle of incidence? Not at all! Depending on the interplay of the ball's spin
and speed and the force of friction, the ball's behavior after the bounce may
differ dramatically. Surely some experienced racquetball, ping-pong, pool,
tennis and players alike take advantage of this fact. A physics teacher, in
turn, can take advantage of the fact that by observing the bounce of a ball her
students can determine the coefficient of friction between the ball and the
floor. All it takes is a typical video (smartphone) camera and some standard
software
  However, this seemingly straightforward method may lead to surprises. If one
wants to double check the value of the coefficient of friction by observing the
second, third etc. bounces, one may find the the force of friction "does not
turn on". We investigate why this happens, state a hypothesis and run some
testing experiments. Teachers who would like to include an illustration of the
scientific cycle at work in their classes may find this paper useful.
