Steve Nash may not be a physicist, but he implicitly understands the deep inner-workings of basketball. While basketball may be unique as a game, the movement of both the balls and the players fall under the laws of motion. Using the laws of physics, an astute basketball fan can scientifically analyze the game, predicting where the ball will go and what will happen to it. Basketball players are truly physicists in action.
The Three Laws of Motion
The three laws of motion, as formulated by Sir Isaac Newton, give the overall context of the happenings in a basketball game. The first law states that objects have a natural tendency to remain on course in their path of motion; that is, without interference an object will continue moving along its current path. The second law states that it takes more force to accelerate an object of greater mass; in other words, more strength must be applied to change the motion of a heavier object. The third law states that every action has an equal and opposite reaction, which means when you apply force to an object, that object also applies force back at you. All actions in a basketball game can be seen in the context of these three laws.
The basketball, the center of the game, is almost continuously in motion. According to the first law, the basketball is always moving in one direction, unless acted on by another force. Essentially, this tells us that the ball is only being controlled by its environment: the players, the floor, the backboard. Unless in contact with one of these forces, the ball will simply continue moving in one direction. The second law, in combination with the fact that the basketball is one constant mass and weight tells us that the more force applied to the ball, the faster the ball will accelerate, or travel. Stronger players can therefore throw the ball faster. The final law of motion describes the bounce of the ball. Whenever the basketball hits anything, that thing pushes the ball back. Because the third law states that the force is equal and opposite, we can know that the ball will return in the direction whence it came and with a nearly equivalent speed.
People themselves fall under the power of the laws of motion. The first law shows that basketball players running in one direction on the court will have a tendency to remain moving in that direction. To stop, they will need to apply force, both internally via muscles and externally via footwork. The force that they apply to the floor in the attempt to stop will be returned to them, pushing them in the other direction and effectually stopping their movement; this is what the third law tells us. The second law shows us how the combination of mass and acceleration multiply to create a bigger force, which can explain why heavy players such as Shaquille O'Neal are dangerous when moving fast.
Gravity is a force of downward acceleration that is constant throughout a basketball game. Acceleration is the key force that causes the basketball to naturally move toward the floor, as shown by Newton's first law. The second law of motion shows that while gravity is a constant acceleration, adding a larger mass to the equation still gives way to a larger force. For example, a hard ball bounce will apply additional acceleration and force to an already downward-moving basketball.
The floor, seemingly unimportant in the laws of motion as it does not move, is actually a significant player in a game of basketball. This is true mainly because of the third law: an equal and opposite force is applied to any force that makes contact with the floor. This is why balls bounce higher when they are moving at a greater speed; the floor pushes the ball back. This is also why players get injured after falling; in an intense basketball game, players fall with much force, which is in turn pushed back upon the players' bodies with an equal amount of force.