The fuzz on a tennis ball can be a real aerodynamic drag, but that’s not a bad thing.
Gravity and the flow of air that surround a tennis ball determine its trajectory, or flight. Like a boat moving through water, a ball moving through the air leaves a wake behind it. The larger the wake, the more drag on the ball and the slower the ball moves. The felt surface of a tennis ball helps a player control the ball's lift and drag, and the way high-speed shots hit their racket. The “fuzzy” surface helps control the bounce, speed and lift on shots, making it easier to return a serve.
Newton's Second Law of Motion
Force, and Newton’s Second Law of Motion, need to be with you to hit a successful forehand.
Newton’s Second Law of Motion explains that
acceleration is created when a force acts on a mass. The mass of an
object determines how much force is required to accelerate, or move it. In the
case of a forehand, the mass is the ball and the racket hitting the ball creates force. The tennis ball then accelerates, or flies across the court. A
tennis player can win more points if they know how to control the speed and
direction of the ball. Since the mass or size of the ball does not change, a
player can control shot placement by adjusting the force of their forehand swing,
which will adjust the acceleration of the ball.
When a fast serve isn’t enough, use the Magnus Effect to keep your opponent guessing about how the ball will bounce.
If you rely on a fast serve to win every point, your opponent may anticipate where your serve will land in the service box. Keep your opponent guessing by putting spin on the ball. A spinning tennis ball moving through air produces a difference in air pressure from one side of the ball to the other. This is called the Magnus Effect. When there is a difference in pressure acting on a ball it creates a net force that will curve the ball away from the high pressure, toward the low pressure side. The resulting bounce will create angles that will keep your opponent guessing every time.
How can the ground and your legs help you hit a
winning backhand? Use them together to start a powerful chain reaction.
Did you know the ground is where a great tennis stroke
begins? It's the first link in a chain reaction, something we call a kinetic
chain of energy transfer. When a tennis player’s legs push into the ground, we
know from Newton’s Third Law of Motion that the ground will push back with an equal
force. The energy from that force goes into the tennis
player’s body. The ground reaction forces are transferred
up the kinetic chain into the player’s legs, hips, torso, arm, hand, racket and
swing. A successful transfer of energy leaves a player with a lot of racket
speed and a great backhand.
Hit or Drop a Tennis Ball
Potential and Kinetic Energy
When you apply the kinetic energy of your swing to a tennis ball, you release the ball's potential energy.
A tennis ball has energy. This energy can change from potential to kinetic energy. When you hold a tennis ball in the air, when it is not moving, it is filled with potential energy. When the ball falls, when it moves and gains speed, it loses potential energy and gains kinetic energy. The same is true of a tennis player’s arm and the strings of a racket. When the player’s arm and the racket are not moving they store potential energy, or more specifically elastic potential energy. When the player swings their racket they transfer the elastic potential energy stored in their arm and the racket’s strings to the kinetic energy of the moving ball.
Tennis Ball Hitting a Court or Racket Strings
Can a tennis court be slow? It depends on how friction
Any time two surfaces rub against one another they create friction. Friction is a force that can slow or stop the forward
motion of another moving object. In tennis, when the surface of a tennis ball rubs against the strings of a racket or a tennis court, friction is produced and
the motion of the ball is changed. If a player calls a court slow, they mean there is a lot of friction created when the ball skids on the court. This
friction can create spin on the ball, slowing its forward speed and making a low bounce. If a player learns how friction affects the ball when it hits the court, they can use friction to their advantage to keep the bounce of their shot low and win the point.
Give gravity a hand. Help your next shot easily clear the net, dive downward faster, or bounce low by applying topspin
When you hit a tennis ball, gravity will naturally pull it to the ground. To hit a winning tennis shot you will want to confuse your opponent and make the ball drop quicker than expected, or bounce low and slow on the court. To do this you need to change the way the ball moves through air molecules; angle your racket
head as you brush up over the ball and make it spin. When the surface of a spinning ball, especially a fuzzy ball, comes in contact with air, friction is created between the air and the surface of the ball. Friction creates unequal air pressure around the ball, changing its trajectory. Adding topspin to a ball forces the ball’s path down while adding backspin forces the ball up.
The Strategy of Placing Shots
Now that you can hit with spin and power, use geometry to place your shot where your opponent can't return it.
The trajectory, or path, of a tennis ball, the shape of a tennis court, and where a player stands on a court all involve geometry. Whether you're focused on offense or defense, you want to control the court and geometry can help you do that. When you hit a shot, you want a bigger target area. When your opponent returns a shot, you want to decrease the size of the area they can aim at. How do you do that? Play the angles. Offensively, a diagonal cross-court shot makes the court 10% longer than hitting the ball down the line. Defensively, moving forward on the court will cut off the angles available to your opponent. If you want a strategic advantage over your opponent, play the angles and study geometry.
A Player's Movement on the Court
In the blink of an eye, a tennis player has to: get in position, take their racket back, control their balance, strategize shot placement and strike the ball. Any interruption to these movements will result in an unforced error. Biomechanics keeps all of these movements coordinated.
Mechanics is the branch of physics that studies the
actions of forces. On a tennis court, where bodies rotate to return a forehand and arms twist to hit a serve, we also need to look at motion. Kinematics is
the part of mechanics that helps us do that. Kinematics gives us math formulas and equations that help a tennis player understand how to
coordinate the acceleration, velocity and distance of a traveling ball, as well as the total time a ball takes to travel across the court. Kinematic equations are mathematical
formulas that we can use to plan more efficient chain reactions of the body, a racket and a ball. Hitting a ball with proper timing, good balance and a relaxed, fluid motion, will not only result in a great shot, it will help prevent injury as well.
For Parents & Educators
Behind every top seed and grand slam, STEM is at play. Explore the science of the game with your kids by graphing the tennis court, simulating a kinetic chain reaction with everyday items, and more.