Physics of Sports
...run as long as they can at a comfortable pace, as opposed to sprinters, who accelerate in an all-out effort for the entire distance of the race. One way to look at the sprinters acceleration is by looking at a velocity curve, the way that the sprinter’s velocity changes from start to finish. This graph is known as a velocity vs. time graph, so one that that looks at it can see how the velocity changes as time goes on. Chapter one is a very important chapter dealing with the concept of motion. Another extremely important chapter to the book is “What Makes Thing Move?” This chapter describes the causes of motion, the concept of inertia, forces, forces and motion combined, and action/reactions. Brancazio can credit Isaac Newton for explaining the causes of motion. Newton figured out that constant-velocity motion is natural motion. Accelerated motion is forced (violent) motion. This can be put into better terms using Newton’s laws of motion: “It is the natural tendency of any object to maintain a state of constant-velocity motion, which can be changed only by an externally applied force” (62). This leads to a very important concept, the concept of inertia. The concept of inertia is the natural tendency of objects to remain in motion. These first chapters sum up background information to physics in a very good manner. Having this out of the way, Brancazio sums up how many sports are used in physics: Basketball In basketball, there are many concepts that can be related to physics. The main one is the science of shooting a basketball. Within this, the idea of projectile motion is very important. When studying projectile motion, we are interested in three aspects of the trajectory: maximum height, horizontal range, and the time of flight. Brancazio puts basketball shooting in very simple terms: “To shoot a basketball successfully one must launch the ball on a trajectory that will make it pass through an 18-inch diameter hoop mounted 10 feet above the floor” (307). There are many types of trajectories that can be used in basketball, and this all depends on the shooting style of the player. There is the low-angle, flat-trajectory, the “line-drive” shot, and there is the steeply angled, high-arching, “rainbow” trajectory (308). Using force, which is any action that can cause an object to accelerate (65), a basketball player can either exert a large force or a minimal force on the ball. The best shooters, the one’s with the softest touch, or the ones that exert the least force with the best arc, are the ones that have the highest shooting percentages. Some advice Brancazio gives is to avoid line-drive shooting, aim high so the ball descends into the basket, and use correct backspin on your shots to help with bounces on the rim or off the backboard (which will be talked about later on) (313). Tennis There are two main ideas of physics that relate to tennis: The Backspin and the Topspin. First, backspin is a very important spin dealing with a sport with any kind of ball. With this, and all spins, you first describe the cause and the effect of the spin. When hitting backspin, the cause of this is angling the racket downward, hitting downward and moving your racket forward. This shot is also known as a slice shot, because of the motion of the swing. Having that said, the effect of the backspin is what is most effective in tennis. When the ball hits the ground, there is a friction force at the point of contact. The ball, for instance, may be moving at 30 mph, but the ball may have a rotation at 2 mph, so the ball hits the ground with a speed of 32 mph. The friction force will have more of an affect because of the loss of forward speed with the ball rotating backwards; the ball will take a lower bounce and lose speed (94). The other important spin is the topspin. In order to create topspin, you brush the racket against the bottom of the ball, turn your wrist hard, and really follow through on your swing. Because of the forward rotation, at the point of contact with the ground, the ball takes a huge bounce, and seems to have lost less speed then thought by the opponent, but it has not gained speed. With more topspin and less force applied to the swing, the rotation speed is greater than its linear (how hard the ball is it) speed, it will accelerate due to the friction force of the ground, and gain speed as it bounces (97). Sweet Spots Golfers, tennis players, and baseball players are all very familiar with the sweet spot. If they aren’t, they should be. The sweet spot is the part of the club, racket, or bat where wherever there is contact made, the ball seems to jump off the surface, there is almost no sensation at the hand, no tugging at the grip, the collision feels smooth, effortless, and true (234-235). Brancazio explains that there is scientific explanation behind this. Physicists have developed a name for the ...