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OBJECTIVES:
A mathematical relationship exists between tennis racquet head speed and the speed of the ball it strikes. Additionally, specific motion patterns are associated with different tennis serve techniques (flat/first, slice, American kick).
You will:
capture the serve motion of a tennis player with a digital or
video camera;
using a transparencies OR a software package analyze the speed, acceleration, displacement and time of the racquet head and ball in the tennis stroke;
compare this player's stroke pattern against a stroke pattern of a professional tennis player.
Alternately,
you can write your own lesson using the motion of a different sport or athlete: swimmer, baseball, football, or basketball players,
gymnast, English jumping, etc.
STEPS TO FOLLOW:
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Review the information in the
background section.
(The background section
is five pages long.
Continue to click "Next Page" to see all five pages.)
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At a tennis court, measure the length of the baseline to the center line.
The tennis player will stand near the centerline of the service line. Measure the length of the player's racquet. Measure the height of the player. Measure the player's extended arm. Measure the head of the racquet, both horizontally and vertically. Measure the circumference of the tennis ball.
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Length |
Baseline To Service Line |
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Racquet Length |
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Player Height |
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Player Arm |
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Racquet Head - Vertical |
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Racquet Head - Horizontal |
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Ball Circumference |
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You will examine a flat 1st serve, a slice serve and an American kick serve.
Set the camera and tripod near the intersection of the sideline and baseline. Film the player doing two flat 1st serves, two slice serves and two kick serves.
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Bring the tripod and camera to the other end of the court. Lower the tripod or sit near the sideline. Film a ball bounce. The angle and speed of the ball will change before and after the bounce.
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If you are using motion analysis software you will follow the software's directions on how to analyze speed and direction.
If you are not using motion analysis software you can use transparencies to mark the player's or ball's motion. Attach your video or digital camera to your computer or another screen device like a television. (This will vary based on the camera and device that you are using. Subsequently, you will need to determine your individual requirements.)
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MATERIALS:
Video Or Digital Camera
Tape Measure
Tennis Court
Tennis Ball
Tennis Racquet
Protractor
Ability To Play Back The Video Or Digital Footage
Either
5 Transparent Sheets (Transparencies)
Different Colored Pens
Transparent Tape
OR
Motion Analysis Software Such As Measurement In Motion Or Dartfish
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Tape the corners of a transparency over the computer monitor or television screen.
Play back your video of the 1st serve. You may want to watch this several times. Experiment with the "pause" or "stop" feature on your video/digital camera, television or computer's video playback control.
Using a colored pen, place a dot on the transparency which corresponds to the tip of the racquet head in the first frame of the footage. Use a different color pen for the ball. Advance one frame and mark the transparency again. Continue until you have completed the entire serve.
Repeat this for the other serves, using a new transparency and a different color pen.
Compare the patterns on the transparencies. What do you notice?
Compare these patterns to the
serve patterns of tennis
professional Pete Sampras.
Tennis Player Serve Pattern
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Based on the footage, how far did the ball travel? If you measure the distance on the computer screen with a ruler, it will only be a few inches. But you know the height of the player and the racquet length. Measure the length of the racquet on the computer's screen (or television). Now you have a ratio: the length on the screen versus the real length. Use this proportion to determine the distance the ball traveled.
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Play back the footage of the ball bounce.
Record the path of the ball before and after the bounce onto another transparency. Use the protractor and record the angle the ball makes with the court before the bounce. Record the angle the ball makes after the ball bounce. Is the ball spinning before the bounce? Is the ball spinning after the bounce? Why?
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