Discussion Questions are meant to be completed when they are reached in the reading, before continuing.  Getting the "correct" answer to Discussion Questions is not important.  Instead, the purpose of Discussion Questions is to address the issues, start you thinking about the material, and identify your preconceptions.  Completing these assignments before continuing with the reading will aid you greatly in the learning process.

How do tennis players know which way a ball will go after it bounces?  Does it bounce back at the player who hit it?  Is it completely unpredictable?  Which (if any) of the colored arrows in the diagram to the right indicates the path the ball will take after it hits the ground?  How do you know this? What rule could you envision that would describe the ball's behavior? In the diagram to the right, the dashed line represents the "normal" to the surface.  The "angle of incidence" the ball makes with respect to the normal on its way toward the surface is labeled as θi.  Why might the angle between the path and the normal provide a better description than the angle between the path and the surface? Sometimes in a tennis or baseball game, the ball seems to go in a direction the player chasing the ball does not expect.  Is this unexpectedness always due to a player's ineptitude, or could there be some other reason for the error?

 

Go to the next page to find out why that angle is measured  to the normal rather than to the surface!