Club-ball physics
Ball in flight
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[Physics of the Golf Club]
     The advancement of golf clubs goes hand-in-hand with the advancement of golf balls. As ball designs began straying from harder wooden construction, golf clubs were no longer expected to have to withstand the impact of a hard wooden ball. This allowed golf clubs to be constructed from newer materials and with different designs. Here are a few examples of some early golf clubs:

(http://kingfish.coastal.edu/physics/projects/2000_Spring/golf/)      Of all the materials different club makers and designers used, iron was found to be the best material for a golf club and is still widely used today. Of course, today there are graphite shafts and titanium clubs as well, but these are fairly recent developments, and mainly reserved for the more pricey drivers.
     As everyone knows, there is not simply one club used for the entire game of golf. There is a huge assortment of clubs, each for a different purpose and to be used in a different situation. A common set of clubs may contain several drivers (with varying weights, head sizes, and lie angles), 2 through 9 irons, a pitching wedge, a sand wedge, and a putter. The drivers have a club head significantly heavier than that of any of the other clubs. These are generally used for the first shot of the hole and will hit the ball the furthest due to a larger transfer of energy from the more massive club head to the ball. The drivers also have a shallower lie angle (the angle between the club shaft and the club face) than most of the irons, but there is some flexibility in the angles amongst different drivers for different length fairways. The irons are ranked from 2 to 9 and the lie angle becomes greater with each. The lower irons are used to hit the ball further while still a ways from the green while the higher irons are used to hit the ball higher with a shorter horizontal displacement. The sand and pitching wedges are designed for chip shots where you are quite close to the green or simply need to get out of a deep sand trap. These clubs allow for a very vertical shot with minimal horizontal displacement. The putter has no lie angle and is simply designed to keep the ball on the ground as it travels across the green, hopefully ending up in the hole.
     Different clubs have different shaft lengths which also affect the flight of the ball, in addition to simply accommodating people of different heights. When looking at the face of a golf club you will notice that there are grooves running horizontally across the club face. The purpose of these grooves is to grip the ball during the impact and impart a backspin on the ball which will help the ball gain loft and remain in the air for a longer period of time. This is discussed in more detail in the club-ball interaction and aerodynamics sections.
     With the improvement of technology, newer and better golf clubs are being released. However, not all of these clubs are endorsed by the USGA. Some of them, such as hollowed out titanium clubs, have a higher coefficient of restitution and impart a greater force on the golf ball. For this reason the USGA has declared that clubs with a coefficient of restitution greater than 0.83 are not approved. A coefficient of restitution of 0.83 means that a ball traveling at 100 M.P.H. will rebound off a metal plate at 83 M.P.H.