The Physics of Tennis

The Physics of TennisBy Adelina Rolea YB

Why I like TennisTennis is a very simple game to play. You dont have to constantly run the entire time, though running is still an important part of playing. I like how you can exert a lot of force into one big hit and then watch how far the ball goes. I dont play tennis right now, but I think I might play in the future.Brief History of TennisDuring the 1100s-1200s the French created the game known as jeu de paume,meaninggame of the palm, where the players batted a ball back and forth with the palm of their hand. However, Major Walter Clopton Wingfield of England is generally considered the father of modern tennis. Wingfield patented tennis equipment in 1874, which included wooden tennis racquets he created. The game of tennis has greatly changed since then. Today, tennis players use racquets with a frame made of graphite and fiberglass and a face made of nylon or other synthetic material. The main goal of tennis is to score more points than the opposing player/team and eventually win the match.Tennis Court Diagram and Dimensions

ForecourtBackcourtNetNetService LineCenter MarkLeft Service CourtRight Service CourtBase LineSingles and Service SidelineDoubles SidelineAlley11m23.8m6.4m4.1mHalf-Court Line1.4m8.2m5.5mSpeedSpeed is the rate of which an object moves. In order to calculate the average speed of an object, you need to determine the distance it stopped at, and the total time it took to get there.The equation for finding speed is:I would measure the average speed of a tennis ball in a game of tennis by meters per second (m/s). This measurement would be appropriate because the length of a tennis court is 23.8 meters, and the time it takes for a tennis ball to travel in tennis is pretty quick, so seconds would be fine. The player controls the speed of the ball by deciding how much force to strike the ball with. The more force that is applied to an object, the father it will travel in a shorter amount of time. In other words, more force means more speed. For example, the player may try to use more force when serving they ball. That way, it will be much harder for the opposing player/team to return the ball. The player controls the speed of the ball and can manipulate it to score a point.

Distance-Time Graph

This is a simple distance-time graph showing a serve of a tennis player, and the return hits after.Player 1 is about to serve the ball. The ball is not movingThe ball is positively accelerating across the court and over the net from the force that was used to launch it.The ball is negatively accelerating from the forces of gravity and friction as it nears Player 2.Player 2 returns the ball toward Player 1, making the distance the ball already traveled, decrease.The ball is negatively accelerating from the forces of gravity and friction as it nears Player 1.Player 1 moves up the court to return the ball toward Player 2, just as before.

VelocityVelocity is the direction an object travels at a speed. For example, if a ball traveled 10 meters in 2 seconds heading South, the balls velocity would be 5 m/s South (10m2s=5m/s). In a game of tennis, the player decides the speed and the direction in which to hit the ball. The player uses the balls velocity to figure out where to direct the ball and how fast it will get there. This is a picture showing a tennis balls velocity. The ball is traveling across the court after being struck by one of the players.The player could try to use less force when serving the ball in certain direction. That way, when the opposing player/ team returns the ball, the player may use a lot of force to serve the ball in the direction away from them. The player controls the velocity of the ball in many ways and can manipulate it to score a point.AccelerationAcceleration is the change of velocity over time, and can be negative or positive. Positive acceleration is the same as speeding up, while negative acceleration is the same as slowing down. To find the acceleration of an object, you must find its beginning velocity, ending velocity, and the total time it took to begin and end.The equation for finding acceleration is:The unit for acceleration is , but it can be measured with any units for speed and time.Positive acceleration occurs when the tennis ball is first struck and the ball speeds up. The player needs this acceleration so the ball will make it over the net. The ball will not stay like this, though. The forces of gravity and friction cause the ball to negatively accelerate. The ball doesnt completely stop moving because the opposing player/team will either have returned the ball by then, or the ball will have scored a point and hit the wall.

ForceForce is a pushing or pulling action that is usually measured by units called Newtons (N). When a tennis player serves the ball or returns it, they apply force when they swing their racquet. This force is transferred to the ball when it makes contact with the racquet. The force pushes the ball through the air, but the ball does not continue to travel straight forward because of outside forces interfering. The forces of gravity and friction are what cause the ball to curve downward in the air and then bounce back up.

This is an animation displaying the forces that take place when a tennis ball bounces on a tennis court. Gravity pulls the ball down, friction pushes the ball back, and the applied force moves the ball forward.

GravityApplied ForcedFriction

9FrictionFriction is a type of force that affects motion when two objects rub against each other. There are four main types of friction, sliding friction, rolling friction, fluid friction, and static friction. Sliding friction occurs in tennis when the players sneaker rubs against the ground. This friction is definitely wanted because it allows the player to run across the court without sliding and slipping. If there was no sliding friction, the player would not be able to play properly. Fluid friction occurs when the ball is traveling in the air. This friction pushes back the tennis ball in the air and causes it to slow down. This is also called air resistance. This friction is wanted. Without fluid friction (along with gravity), the tennis ball wouldve traveled in a straight line at a fast constant speed. Also, there would be nothing to slow down the ball that would still be traveling at the high speed it was struck by, so the ball would be very dangerous. Friction keeps tennis fun and functional.GravityGravity is a type of force that pulls objects together. Every object has gravitational attraction, and the greater the mass an object has, the greater the gravity it has. The earths gravitational pull is so large that our gravitational pull doesnt affect any other objects. The earths gravity pulls down any object toward its center. Without gravity, nothing would be kept down, and tennis balls, racquets, players, and everything else would all float away somewhere. During a game of tennis, gravity is essential, as it affects the path the tennis ball travels while in the air. Gravity pulls down the ball and causes it to curve downward in the air, hit the ground, bounce up, and continue moving until it is returned by the opposing player/team or passes and becomes a scored point.Newtons First Law of MotionNewtons First Law of Motion states that an object in motion will stay in motion until acted upon by another nonzero force. During a game of tennis, a tennis ball would be served, and then would continue in a straight line, if not for the forces of gravity and friction. The earths gravity causes any object to be pulled towards earths center, including a tennis ball. Gravity pulling the tennis ball down causes the ball to curve downward in the air and slow down as well. Fluid friction is the other force that pushes back the tennis ball and causes it to slow down. This is also called air resistance. Without these external forces, the tennis ball would travel in a straight line for infinity.Newtons First Law of Motion also states that an object at rest will stay at rest until acted upon by another nonzero force. When a tennis ball is about to be served, the ball is first at rest. When the player throws the ball in the air, the ball is no longer at rest and is motion. Then, gravity pulls the ball back down and the player hits the ball, propelling the ball forward.Newtons Second Law of MotionNewtons Second Law of Motion states that an objects acceleration depends on its mass and the net force acting on it. In a game of tennis, the mass of a tennis ball will always stay constant. The only variable in a tennis balls acceleration is the net force acting on it. When the player strikes the ball in a service or return, theres more force applied than the friction slowing down the ball. This causes the ball to positively accelerate forward. As the force from the players strike starts to deplete, since the force is being used to keep the ball moving forward, the forces of gravity and friction increase on the ball. Gravity and friction both pull the ball both downward and push it backward while the force in the ball continues to move forward. The result is the balls path curving downward in the air and negatively accelerating.

Force AppliedForce AppliedThese are two different pictures showing Newtons Second Law. In both pictures, the ball has the same mass, but the force used is different. On the left, more force is used, so the balls acceleration is greater. On the right, less force is used, so the balls acceleration is less.Newtons Third Law of MotionNewtons Third Law of Motion states that if one object exerts force onto another object, then the second object exerts a force of equal strength in the opposite direction of the first object. A tennis ball being hit by a tennis racquet is an example of this. In order to serve or return the tennis ball, the player must exert force onto the ball by swinging the tennis racquet. When the ball comes into contact with the strings of the racquet, the force the player used to swing the racquet is now exerted onto the ball. The ball now exerts a force of equal strength in the opposite direction of the racquet and travels through the air. When the balls path starts to curve downward from the forces of gravity and friction, the ball will make contact with the ground. Although the ball exerts force onto the ground, the earth mass is much greater than the tennis balls, the force is exerted back into the ball and the ball continues forward.

This is a picture depicting Newtons Third Law. When the tennis player strikes the ball, the force from the hit is transferred to the ball, giving it enough force to go into motion across the court.Work and PowerWork is how much force is used to move an object and is measured by units called Joules (J). The equation for finding work is:

In a game of tennis, a player can do work by launching the tennis ball with enough force that the ball travels a distance across the court and over the net. For example, if a player were to hit a tennis ball with a force of 30N and the ball traveled 15m, the total work done would be 450J (30N x 15m = 450J). If a player were to hold a ball in the air, that would not be categorized as work. Although it does require force to hold up the ball, the ball did not move a distance, therefore no work was done.

Power is how much work is done in a certain amount of time and is measured by units called Watts (W).The equation for finding power is:

In a game of tennis, a player can use power to launch the ball across the court in less time. The more that is used, the more work will be done in less time. For example, if the player were to launch the ball over the net with 450J of work in 3 seconds, the total amount of power done by the player would be 150W ( = ) .

Simple MachinesA Simple Machine is a basic device used to make work easier and done with less power required. Some examples of simple machines are pullies, gears, wheels and axles, wedges, inclined planes, levers, and screws. In the left picture, the players arm holding the racquet acts like a third-class lever. A third class lever increases distance, but doesnt change the direction of the input force. The players wrist joint acts like a fulcrum, the fixed pointthat a lever pivots around. The force the player uses to swing the racquet is the input force, and the output force from that exerts onto the tennis ball, causing the ball to fly in the direction it was aimed at. Another simple machine used in tennis is the shoelaces on the tennis shoes of the player. The laces act like a pulley and keep the tennis shoes securely on the player. When you tug on the laces of the shoes, they move through small holes which reverse the direction of the force and pull the shoes tightly around the feet. The tennis shoes are part of the sliding friction that help the player have traction when they run, and the shoelaces help keep them on.

FulcrumInput ForceOutput ForceWorks CitedPictures: Tennis Flat Serve. Digital image.Optimumtennis.net. N.p., 2009 - 2013. Web. 22 Apr. 2013. . Tennis Court. Digital image.Greycollege.co.za. Grey College, 2008-2012. Web. 22 Apr. 2013. .

All other pictures used were taken from Microsoft PowerPoint Clip Art or made by Adelina Rolea

Information: Evert, Chris. "Tennis."World Book Advanced. World Book, 2013.Web. 22 Apr. 2013..