Accuracy of flight requires straightness in an arrow throughout its 24 to 30 in. of length. Feathers are commonly used as stabilizing vanes to keep the shaft tangent to its trajectory. Because of their natural warp, they cause the arrow to spin, which partly compensates for lack of straightness. The wood of which an arrow is made must, obviously, be strong and tough to withstand impact and other forces without damage. Only a few kinds of wood are suitable because, in addition to strength and toughness, arrows require a high ratio of stiffness to density. In hunting arrows strength is the first requirement and the stiffness-density ratio is less important. Differences in mass produce differences in velocity in arrows shot from the same bow. Hence it is necessary for accurate shooting, when a number of arrows are used in the same set, that they have the same mass. Not only this, but they must have the same dimensions and form, and the same mass distribution. The reasons for these requirements will appear in the subsequent discussion. In recent years good arrows have been produced of steel and aluminum alloy tubing.
Accuracy in the shooting of successive arrows requires not only the aforementioned uniformity of characteristics, but also that the bow have an unvarying force-draw characteristic so that the total energy for propelling the shaft is the same in each shot. The limbs of the bow must work together and without variation in their mode of motion in successive shots. Finally, the 17 things essential to good shooting—which are distributed among the five principal acts of standing, nocking,  drawing, holding and loosing—must be done in precisely the same manner each time to achieve a perfect shot. Hot. Sultry weather may affect the bow—and the archer—by change of temperature and moisture content. Shooting a bow is a physical experiment, the results of which are most closely reproduced when there are no uncontrolled variables.
The somewhat sketchy information conveyed up to this point may serve to give some appreciation of the fact that the bow and arrow individually, and their use in combination, present a great wealth of problems. We are now prepared to consider those lying in the domain of physics—to indicate what progress has been made in their solution, and how physical research and development have greatly improved the implements of the sport. Applied physics has given archers a weapon of precision, comparable in performance with a target pistol.