Physics Blog 2: Golf

A few weekends ago, I went golfing with some family friends at Mid-Pacific Country Club. Searching my mind and my camera for an idea for this blog, I came across the pictures from that day and was struck by the physics that were obviously involved in golf. In terms of what we're learning now, the golf ball leaves the tee when struck on a vector; in other words, it has both magnitude and direction. This picture is of my friend's dad on the driving range and shows the swing involved in getting the ball going:



Here is a close-up of what happens when the driver contacts the ball as it sits on the tee:



In this picture, it looks as if the ball is taking off at an angle of maybe 20 degrees with the ground. I don't have a way of measuring things like the initial x or y velocities based on this picture, but with my knowledge I would estimate that the ball leaves the tee with an initial overall velocity of about 80 meters per second. Once in the air, the y-velocity of the ball is constantly subjected to the acceleration of -9.8 meters per second squared provided by gravity. However, the x-velocity remains constant the entire time. The ball ends up following a roughly parabolic path; I say roughly because wind and air resistance factor into the actual path the ball takes in the air. Thus, recognizing physics concepts at work in golf is easy once you're familiar with them.

Volleyball Attacking

This past summer, my club volleyball team competed in the USAV Junior National Championships in Austin, Texas. Volleyball, like every other sport, provides a ton of examples of physics at work. Attacking, which is comprised of the setter setting the ball and the attacker hitting it, is one area where it is easy to see physics at work:

When the setter (15) sets the ball, it leaves his hands at an initial velocity, and the moment it leaves his hands it is in free fall. Thus, the ball is going to travel upward, accelerating at a rate of -9.8 m/s squared, reach a peak, and then travel downward, accelerating at a rate of 9.8 m/s squared. It's the attacker's job to hit the ball as close to the peak as possible:

Here the ball is going to leave the hand of the attacker (13, me) at an initial velocity and then decelerate (or have negative acceleration) due to air resistance and move downward (not upward first, since the trajectory is already downward) due to the constant pull of gravity:

During all of this, the actual jumping also demonstrates physics (as we learned in our lab last week). The body is in free fall from the moment it leaves the ground, which results in a symmetrical, parabolic position vs. time graph, just like a volleyball that has been set. In the video linked below, the first clip shows the effect of gravity on jumping; the second clip shows the effect of gravity on setting; and the last clip is just there because Clint has a RIDICULOUS save:

http://www.youtube.com/watch?v=3le-5S6OL7Q

Thus, it is easy to recognize the concepts of physics that are demonstrated in this aspect of volleyball.