Physics of Tennis Racquets :: physics sport sports tennis

Missing figures Tennis racquets with old type of strings did not allow power and control over the racquet at the same time. To get a powerful stroke player had to hit the ball with the area of racquet closer to the tip of the racquet (toe). To obtain control and to reduce vibration of the racquet, player had to hit the ball with the area of racquet called â€Å"sweet spot†, located around the geometric center of the head. NASA’s 1973 Skylab 3 mission showed that tapered strings can move the â€Å"sweet spot† from the center of the racquet toward the position of greater power. The NASA research on spider webs, which was meant to find the solution to reduce the vibration on space stations, unexpectedly benefited tennis. NASA’s Skylab, the first U.S. space station, in 1973 carried out the experiment with the space born spiders Anita and Arabella, to learn from spiders how to construct low vibration space stations. Soviet space station Mir had serious problems with vibration. Every use of exercise equipment caused the entire station to shake. Spiders are well known for making their nets capable to absorb the impact of their pray. According to the book â€Å"The Web of the Spider† by Laura Barr Lougee [3], spider webs are made in such a way to keep all tensions in balance. The NASA research showed that the change in diameter of strings changes the stability of a network. This property of strings was used to improve the performances of tennis racquets. It is hard to define â€Å"power† of racquet. According to [4] power could be defined as 1. racquet bounce (high coefficient of restitution) 2. high swing weight (high angular momentum) 3. low work (racquet which gives the greatest ball speed with a given player effort) The easiest way to understand power is the coefficient of restitution (COR). The maximum power occurs when the COR is the greatest. The coefficient of restitution is the ratio of the differences in velocities before and after the collision. COR is defined as difference in the velocities of the two colliding objects after the collision, divided by the difference in their velocities before the collision. COR = coefficient of restitution = linear velocity of the racquet mass center before impact = linear velocity of the ball before impact (will be negative according to our convention that away from the player is positive)