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Tennis racquet string tension and ball speed Featured science projectScience project video


The materials required for this science fair project:

-    5 amateur tennis players
-    1 tennis court
-    2 tennis racquets,  both with frames of the same weight and design.
-    1 box of tennis balls
-    Radar gun to measure speed (may be purchased from radar gun suppliers such as Radar Sports)


1.    For this science fair project, the independent variable is the tension level of the string in the racquets – 50lbs or 70lbs. The dependent variable is the resultant velocity of the ball, determined  using the radar gun. The constants (control variables) are the skill of the tennis player, the weight of the racquets, the stiffness of the racquet frames and the type of tennis balls used.

2.    The strings on the 2 tennis racquets are adjusted so that the first racquet will have  a string tension  of 50 lbs while the second racquet will have  a string tension  of 70 lbs.
3.    The tennis players are allocated a number 1 to 5 and asked to warm up before the experiment is started.

4.    The 1st tennis player is  asked to serve the ball using the racquet with 50 lbs string tension. The speed of the ball after the serve is measured using the radar gun. The ball is served 5 times by the same player and the maximum speed reached is recorded in the table below.

5.    The first tennis player is next asked to serve the ball using the racquet with 70 lbs string tension. The serve is again performed 5 times and the speed is measured using the radar gun. The highest speed  observed is recorded in the table below.

6.     Steps 4 and 5 are repeated using the remaining 4 tennis players, and the maximum speed  reached by the ball  out of each of the 5 attempts by the same player using the same racquet is recorded in the table given below.

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Complexity level:
Project cost ($):
Time required:
1 hour to prepare, 6 hours for this science project experiment
Material availability:
You will need a radar gun. Their prices vary tremendously (some cost a few hundred dollars), but a fairly cheap and effective model is the Bushnell Speedster II - it should cost less than $100
Safety concerns:

Basic safety requirements