SCIENCE CONCEPT:
- When a ball bounces on the court, its speed
is reduced significantly by its interaction with the court surface. When
the ball slows down a great deal after it bounces, the court is called
slow. A fast court does not slow the ball down as much. There are two
things that affect the court's speed: The coefficient of
restitution (COR) and the coefficient of friction (COF).
The COR
characterizes how high the ball will bounce if you drop it from a given
height. The high COR court surface gives the ball a higher bounce. The
low COR surface gives the ball a lower bounce. The COR is defined as the
ratio of the vertical ball speed after the bounce to the vertical ball
speed before the bounce. The COF is the measurement of the frictional
force of the court surface on the ball. This is in a direction parallel
to the surface. Friction slows down the ball. A high value
of COF indicates a high frictional force on the ball.
STUDENT OBJECTIVE:
- The student will demonstrate and observe how these
two coefficients (COR and COF) affect the ball as it bounces on the
court.
OVERVIEW:
- The student will use a step ladder and tennis balls to observe
the restitution and friction effects. Each student will take a turn standing on
different step levels of the ladder and drop the ball onto the surface of
the court at different angles.
They will observe how the ball reacts at different heights as
it is dropped onto the court. Have the students drop the ball slowly and
quickly to see the variations. Ask the students to graph their
findings.
TEACHER TEXT:
- The horizontal speed of the tennis ball is
affected more by the friction than by the COR. While the COR does
influence the vertical speed of the ball, the friction affects the
horizontal velocity of the ball. The horizontal velocity is what
determines the speed of the court.
The greater the friction between the ball and the court,
the slower the ball will be after it bounces. The greater the friction,
the slower the court.
If the ball leaves the court before rolling begins, the court is
considered fast. Vertical speed loss is affected by the COR.
In terms of science, the laws of physics how fast or slow a court is.
|
|
PREPARATION TIME:
- 15 minutes.
LESSON TIME:
- 60 minutes.
TEACHER PREP:
- Gather materials
WORDS TO KNOW:
- coefficient of restitution(COR)
- coefficient of friction(COF)
- horizontal speed
- vertical speed
- frictional force
- rotation
- rebound angle or angle of rebound
|
