SCIENCE CONCEPT:
- The throwing of a curve ball is literally a snap. A
pitcher makes a finger snapping, wrist twisting movement as the ball is
released. This creates a topspin of the ball as it travels, so that the
top of the ball is moving forward against the air and meeting resistance
while the lower half is spinning backward and moving in the same
direction as the air.
STUDENT OBJECTIVE:
- The student will demonstrate and observe the curve
ball as it is thrown from the pitcher's mound to home base.
OVERVIEW:
- The student will take several turns throwing the baseball with
the finger snapping, wrist twisting movement as the ball is released.
TEACHER TEXT:
- Throwing a curve ball is a snap - literally. A pitcher
makes a finger snapping, wrist twisting movement as the ball is released.
This creates a topspin of the ball as it travels, so that the top of the
ball is moving forward against the air and meeting resistance while the
lower half is spinning backward and moving in the same direction as the
air. The air pressure above the ball is greater than the pressure below,
causing the ball to curve downward. In the 60 foot 6 inch distance
between major league pitcher and batter, this curving force can move a
ball down a foot or more.
Combining with the effect of air pressure is gravity. A
ball will eventually fall to earth as its velocity (speed) is reduced. A
pitcher applies just enough force to his throw so that it is spent as it
reaches the batter, allowing gravity to pull the ball down. Gravity
makes objects move faster over time, so its effect on the ball is more
pronounced as it reaches home plate. A pitch that drops half a foot in
the first half of its flight falls another two feet in the second half.
Add the fact that the pitcher is standing on a mound nearly a foot higher
than the batter, and releasing the ball at head level, and we see that
the arc of a curve ball is significant.
A curve ball, therefore, for the reasons given, is
indeed no optical illusion. Anyone who has stood in a batter's box and
tried to hit one has never doubted that the curve ball curves. But
batters who claim the ball seems to make a sharp bend away from the bat
as the swing, as if wood repelled leather, are somewhat the victims of an
illusion. Studies show that a curve ball makes a smooth, circular path
from pitcher to batter; but because of the increasing gravitational pull
on the ball, and the difference in height between release and arrival,
the ball appears from a batter's point of view to "fall off a table".
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PREPARATION TIME:
- 10 minutes.
LESSON TIME:
- 30 minutes.
TEACHER PREP:
- Gather materials
WORDS TO KNOW:
- topspin
- resistance
- air pressure
- gravitational pull
- 'round house curve ball'
- 'screwball curve ball'
- 'slider curve ball'
- 'sinker curve ball'
- 'knuckleball curve ball'
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