SCIENCE CONCEPT:
- Newton's Laws of Motion defines what happens when a
force acts on an object. The object accelerates in the direction in
which the force is acting. A force acting on a stationary object starts
it moving. A force acting on a moving object will speed it up, slow it
down, or change the direction in which it is moving. A spinning tennis
ball in flight has 3 forces acting on it: lift, drag and its weight. Lift is
generated by the spinning ball - thus balls hit flat (with no spin)
do not generate lift.
STUDENT OBJECTIVE:
- The student will demonstrate and observe the motion of a
tennis ball using a ball and racket.
OVERVIEW:
- The student will hit a series of tennis balls with a racket
and observe how the ball moves from the
time it is first hit until one player receives a point.
Students on the other side of the net will
observe how the return hit on the ball demonstrates
Newton's 1st Law: a force acting on a
moving object will speed it up, slow it down, or change the direction in
which it is moving. The students will take turns being the one beginning
the acceleration of the ball or the one acting on the moving object (the
tennis ball).
TEACHER TEXT:
- The lift of the tennis ball begins when spin is applied by the
racket
to the ball. As well, the ball experiences the effects of weight and drag
throughout its flight. The flight of the ball from one side of the court
to the other takes less than a second.
This happens so quickly that generally the
naked eye can not observe the differences in the trajectories and these effects.
With a time-lapsed camera we can see the effects more
clearly.
Because of the way the ball is initially hit, the return of
the ball will be unique each time. Sometimes the ball will have been hit
with no spin, or a great deal of spin on it. When
the ball bounces on the opponent's court there will be variations because
of the friction of the bounce on the court. The ball will take on a spin
as it rebounds from the court before the opponent returns the ball to the
server. The ball may have a change in direction in which it
is moving.
As each ball is hit, different variables affect
the motion of the ball: the amount and type of spin, the impact
of the ball with the racket, the interaction with the court.
With all of
these variations there is always something new to observe. This is what
makes science and in this case "Tennis Science" so interesting!
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PREPARATION TIME:
- 15 minutes.
LESSON TIME:
- 60 - 90 minutes.
TEACHER PREP:
- Gather materials
WORDS TO KNOW:
- acceleration
- friction
- lift
- variations
- stationary
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