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Right now in physics we are learning about projectiles. So far we have learned that the angle which creates the longest projectile is 45 degrees. But with my golf experience I know that my driver (12.5 degrees) goes the furthest, then my 3 wood (21 degrees) and so on until I get down to my sand wedge (56 degrees) and my lob wedge (60 degrees), which go the shortest. With or without air resistance, how come the 45 degree angle doesn't hold true in golfing? What is the difference?
Question Date: 2005-12-07
Answer 1:

Thanks for the question concerning golf balls and range. It certainly is true that drivers provide the greatest range, with face angles of 10-20 degrees. This seems to contradict the physics of projectiles, which suggest that a maximum range would be achieved with a face angle of 45 degrees.

Several factors make golf more complicated than the physics of projectiles; two of the most important factors are air and the club head speed.

Air plays a very big role in the game of golf. During a tee-off, the golf ball can easily exceed 100 miles per hour. At these speeds, the effect of air is pretty significant (in fact, the reason that the golf ball has dimples is to provide greater consistency and control as the golf ball sails through the air). Because the club face generally imparts at least some backspin during the swing, the velocity of air over the top surface of the ball is greater that the velocity of air over the bottom surface for the duration of the flight. This difference in velocity results in lift, and helps to keep the ball in the air. The same effect is seen if you slice the ball; a component of rotation in a "sideways" direction causes the ball to curve towards either the left or the right. As a consequence, the projectile equations are no longer accurate; golf balls do not follow perfect parabolas during their flight.

Another very important consideration is how fast the club head is traveling when it strikes the ball. You probably noticed that your driver is somewhat longer than your wedges. Longer shaft lengths mean that the club head is traveling at a higher velocity, and consequently, the ball will leave the club face with a higher velocity. Velocity is important for drivers, whose role is to get the ball as far down the fairway as possible. In contrast, wedges are used for more precise shots, where power is not nearly as important as accuracy.

To summarize, the longer shaft length and the lift of air result in the long range capabilities of drivers and woods, despite the relatively small face angles compared with wedges. Spinning and air resistance are so important that the projectile equations are no longer very good approximations for a golf ball.

I hope that answers your question!

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