The Physics of Basketball BY: David Garcia P.5

Dribbling When the basketball falls to the ground or is dribbled (a hand pushes down on the ball) the ball bounces back.  This occurs due to the elastic collision that occurs between the basketball and the ground (or more specifically, the air particles in the ball and the ground).  A perfect elastic collision is defined as a collision of particles in a closed system in which the total kinetic energy of the particles is conserved.  The elasticity of a basketball can be determined by the height the ball rebounds.  The basketball cannot achieve a perfect elastic collision with the ground but it can, however, achieve as much as 80% elasticity depending on the air pressure inside the ball. The air pressure of the ball greatly affects the elasticity of the ball and the conservation of energy of the ball.  A tightly inflated basketball has a large amount of particles present inside the restricted space the surface of the basketball provides.  The picture below represents a tightly inflated basketball.  Although air particles are so small in size that they would not be able to be seen and there would be many more particles present inside a basketball than shown here, we will use this picture solely as a visual aid.

Spin   Since basketballs move at such low velocities, placing spin on the ball does not effect air resistance of the ball to any great extent. Rather, placing a spin on the ball increases the chances of the ball going into the net if it was to touch the rim of the net or the backboard as it often does. When a basketball has spin and hits one or the other, the contact made between the two objects will cause the ball to change its velocity in the direction opposite the spin direction as shown below.

Passing Passing is perhaps one of the most important components of basketball. A game would not be possible without the aid of team work and passing. To successfully complete a pass, there are many factors which the player must take into account. First of all, in order to begin a pass, a player must exert a force of the basketball. Once the basketball leaves the players hands, it becomes a projectile. A projectile is acted upon by two independent forces. The first, the x-coordinate, is the force exerted on the ball by the player. The second force is the y-coordinate, which is the pull of gravity on the ball, approximately -9.8 m/s². Therefore, the ball will travel in a downward parabolic path. In order to compensate for this downward path, the player must throw the ball towards a target located slightly higher than he wishes the ball to go.

Free Throws Free throws in basketball are not as simple as one might expect. In order to ensure that the basketball will fall into the net, one must aim for a spot above the net. This is because of the work of gravity on the ball. Gravity accelerates projectiles 9.8m/s² towards the center of the earth.  As the basketball freely travels through the air it falls 9.8m for every second that it is suspended in the air, and because of this the player must aim release the ball at a precise angle to the rim.     If you were to map out the path of a basketball during a shot, you would see that it travels in a parabola shape. It first is projected above the position it was released at and as gravity acts on it, the ball continually slows in its upward ascent. Once the ball reaches it climatic height (The point at which the force of gravity becomes equal to the original  upward force of the ball, and at which time gravity reverses the direction of the ball), gravity accelerates it in the downward direction and it begins to arc downward. The parabola shape consists of two coordinates, the X and the Y. The X coordinate represents the forward momentum provided to the ball by the player, and the Y coordinate represents at first the upward momentum from the player, and later shows the result of gravity's pull on the ball. Also, because of the constant pull of gravity on the ball, it is essential to remember that one must aim the ball higher than the actual intended target in order to compensate for that pull.     The parabolic shape is comparable to an arc, which is why shooting is dependent upon "the perfect arc". If the ball is simply thrown directly at the basket, and not a little upwards it will not go into the net. By the time the ball travels to the net gravity will have already pulled it downward 9.8m for every second that it was suspended in the air. This is why it is absolutely essential that the ball is pushed up and outward towards the net, as opposed to just being pushed forward.