How Does That Golfball Do It?!

One afternoon this past summer, Justin Park, Shane Hayakawa, Matt Callahan and I decided to go golfing at the Ala Wai Golf Course. As we made our way through the 18-hole course, I would carefully watch my golfball whiz through the air after each drive and would wonder why the ball formed a parabolic path in the air every time that I hit it. After each drive, the ball would continue to increase its vertical position in the air until it reached a peak height, when it would then fall back down to the ground in the same amount of time that it took the ball to reach its highest point. At the same time, it seemed as though the horizontal velocity of the ball was constant. Having already taken AP Physics B, Shane, Matt and Justin already knew the physics behind the golfball phenomenon, meanwhile I on the other hand was missing out on this knowledge. I now, however, educated in the topic of motion, can explain the reasoning behind the golfball’s motion using projectile motion.

A photo of me after pitching my golfball onto the green.

In golf, the golfer hits the ball with a certain initial velocity at a certain angle. Both the magnitude of the velocity and the angle that the golfer hits the ball are very important as they determine the initial x and y velocities, which can then, with time, help to determine how high and how far the golfball will go. The parabolic motion of a golfball is explained by all of these factors in that the ball must reach a peak height in its trajectory before gravity brings the ball back down to the ground. The initial y-velocity constantly decreases because of gravity while the horizontal velocity remains constant because there are no horizontal forces affecting the golfball.

It is interesting to note that the average professional golfer can hit a golfball at around a velocity of 100mph, wow! Knowing this, we can use vectors to find that, if the golfer strikes the ball at a 40 degree angle, the initial (and final because there are no horizontal forces acting on velocity) horizontal velocity is 100mphCos40 = 76.6mph and the initial vertical velocity is 100mphSin40 = 64.3mph. Now those are some fast traveling balls!

Golf, though often touted as a tedious and sometimes boring sport, is actually quite fun when you use physics to analyze the ball’s motion as you play.

Me and Justin riding on a golf-cart after our round of golf.