Newton's Laws
First Law
Newton's First Law or also known as the law of inertia, states that if the net force of the object is zero then the object will remain stationary or in a constant state of motion. When you hit the ball applying the force by the racket, the ball goes flying. Although, without and any external forces acting on the ball, it would continue it's state of motion in the air forever. The external unbalanced forces of air resistance, slowing down the ball, and gravity, which pulls it down, is the reason the ball to come back down to the ground.
Second Law
Newton's First Law states that if the net force of the object is not zero then the object will remain in a state of accelleration using the equation F=ma (force= mass x acceleration). This law applies to tennis as well. When hitting the ball, the racket applies a force onto the ball making it fly to whichever direction, as shown on the right. The mass of the ball remains the same throughought the action, therefore the amount of force exerted on the ball is the main determining factor of the ball's acceleration. The harder the ball is hit, or in other words the larger the force exerted on the ball by the racket, the larger the ball's acceleration will be.
This moving image demonstrates the force applied and the rapid acceleration of the ball, off the racket.
Third Law
Newton's Third Law states that every action has an equal and opposite reaction. When playing tennis, the ball is hit back and forth between players. As the ball comes flying to your side of the court the ball applies the action force by smashing into your racket. The racket then reacts to this action by sending a force back onto the ball making it once again fly to the opposite side of the court.
Action Reaction Forces
The action force in tennis is when the ball impacts the ground after flying. The ground reacts to this impact and pushes a force back onto the ball making it bounce . Depending on the trajectory and speed of the at the landing point will determine how high or low the ball bounces. As seen in the picture to the right, the ball lands and is immediately catapulted of the ground, resulting in the bounce of the ball. The action and reaction forces between the ball and the ground, depending on what type of surface, will determine the effect and quality of the bounce.
Fapp
(action)
Ff
Fn
FBD of ball landing
(reaction)
- In this Free Body Diagram, the action reaction forces of the ball landing are shown. The force applied is the action force of the ball landing. The reaction force is the force of friction applied by the ground back onto the ball, working against the motion of the ball.
This image shows the interaction between the ball and the racket, to demonstrate the action and reaction .
Fg
Friction Forces
The force of friction takes place on numerous occasions in tennis, with racket and ball friction, and air friction, although the most important force is as the ball just makes impact on the ground once it lands. The ball slightly for a fraction of a second slides on the court before bouncing back up. This split second slide significantly slows down the ball as the ground applies a strong force of friction acting against the ball's motion, thus reducing its speed. The picture on the right shows the friction force acting upon the balls motion.
This image represents the bounce of the ball upon landing, with friction force acting against the ball's motion