Chris

[] [] [] [] [] [] http://www.sciencebuddies.org/science-fair-projects/recommender_results.php?pc=1&isb=cmlkOjQyODcyNzAsc2lkOjEscDo3 Objective The goal of this project is to determine whether "corked" baseball bats make the ball travel farther than unaltered wooden bats. Introduction When a batter hits a baseball, what determines how far the ball goes? If you think about it carefully, you can come up with quite a few variables, including: This project concentrates on the first two variables: the speed of the bat and the weight of the bat. When two objects collide, both the speed //and// the weight of the objects matter in determining the outcome. For example, think about marbles. The shooter marble is bigger and heavier than the regular marbles. When the heavier shooter marble collides with a lighter regular marble, the shooter knocks the regular marble a long way. If you do it the other way around, the regular marble doesn't knock the shooter very far because the regular marble weighs less. However, if you increase the speed of the regular marble, by shooting it harder, the increased speed tends to make up for the decrease in weight, and the faster-moving marble will knock the shooter farther. This combination of speed and weight is called //momentum// in physics. Momentum is the product of the mass of an object and the velocity of the object. The variable for momentum is //p//, so the equation for momentum is: //p// = //m// × //v//. Going back to our batter, we can say that the more momentum the batter can create with the bat, the farther we would expect the ball to go when it is hit. To increase the momentum, a batter can use a heavier bat, and/or the batter can also try to swing the bat faster. As the weight of the bat is increased, at some point it becomes to heavy for the batter's muscles, and bat speed decreases. A lighter bat is easier to swing fast, but at what point does the decreased weight make more difference than the increased speed? In other words, what is the best balance between bat weight and bat speed? You may have heard of baseball players "corking" their bats in order to try and hit the ball farther. A "corked" bat is one that has been drilled out at the end, with the hole filled up with cork or some other material, and then capped off so it looks like a regular bat. Because the filling material is less dense than the wood of the bat, "corking" makes the bat lighter. The end result is that the batter can swing the bat faster. But we've seen that decreasing the weight of the bat will decrease the momentum. Can the extra speed of the swing with a corked bat make up for the decrease in weight? That's what this project is designed to find out! Terms, Concepts and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts: Questions Bibliography > Wikipedia contributors, 2006. "Corked Bats," Wikipedia, The Free Encyclopedia [accessed November 6, 2006] []. > Henderson, T., 2004. "Momentum and Its Conservation," The Physics Classroom and Mathsoft Engineering & Education, Inc. [accessed April 18, 2008] []. > Adair, R.K., 2002. //The Physics of Baseball//, New York, NY: HarperCollins Publishers. Materials and Equipment To do this experiment you will need the following materials and equipment: Experimental Procedure Preparing the Bats
 * the speed of the bat,
 * the weight of the bat (including how that weight is distributed),
 * the angle of the swing,
 * exactly where, along the length of the bat, the ball and bat make contact,
 * exactly where, around the circumference of the bat, the ball and bat make contact,
 * the speed and direction of the incoming pitch, and
 * external factors such as wind, air pressure, and temperature.
 * mass,
 * velocity,
 * momentum.
 * Which Goes Further Corked Or Uncorked bats?
 * Here is a good introduction to the subject of corked bats:
 * Here are a couple of interesting sites examining the science of baseball:
 * Staff, 2000. "The Science of Swat," Arizona Engineer Newsletter, College of Engineering and Mines, University of Arizona, Tucson [accessed November 6, 2006] [].
 * Exploratorium, 1998. "Science of Baseball," Exploratorium [accessed November 16, 2006] [].
 * This high-school level physics tutorial has excellent information on momentum and how to analyze collisions between objects:
 * Particularly for more advanced students, we recommend this book, especially Chapter 5, "Batting the Ball," and Chapter 6, "Properties of Bats":
 * 3 (or more) identical wooden baseball bats,
 * drill with 1/2-inch bit,
 * wood vise or clamping jig for holding bat securely,
 * hammer,
 * punch,
 * filling material for bat, e.g.:
 * sawdust,
 * rubber balls,
 * cork sheeting;
 * white glue,
 * permanent marker,
 * baseball,
 * ball tee,
 * tape measure,
 * optional: spring-loaded device for swinging bat, which you design and build; suggested materials:
 * springs to provide power,
 * wood for anchor post, and bat support to hold bat at proper height for batting tee,
 * hinge to attach bat support to anchor post,
 * fasteners for putting the pieces together.

Testing the Bats
 * 1) **Safety Note:** Have an adult drill the bats for you.
 * 2) Set one bat aside and do not drill a hole in it. You will compare the performance of the "corked" bats to this unaltered bat.
 * 3) Use the following procedure for preparing the "corked" bats:
 * 4) Clamp the bat securely in the wood vise.
 * 5) Mark the center of the wide end of the bat (not the handle end), and use the hammer and punch to dimple the wood so the drill bit won't slip when starting.
 * 6) Drill a 1/2-inch diameter hole no more than 6 inches deep, taking care to drill straight along the long axis of the bat. Pull back on the bit occasionally to clear sawdust from the hole.
 * 7) Fill the hole with the material to be tested (e.g., cork or sawdust or rubber balls). Pack the material tightly.
 * 8) Use a permanent marker to label the bat with the filling material used.
 * 9) Seal the end of the bat closed with a wood disk and glue (or sawdust and glue).
 * 10) Allow the glue to dry overnight before performing tests with the bats.

Variations
 * 1) Now you need to test which bat can hit the ball the farthest. For each method that you try (see below), do at least 25 trials with each bat. Measure the distance that the ball travels from the tee until it first hits the ground. Calculate the average distance from all 25 trials. (More advanced students should also calculate the standard deviation.)
 * 2) There are a couple of different methods you could use to perform the test:
 * 3) using an apparatus to simulate a swing with constant force, or
 * 4) swinging the bats yourself.
 * 5) For the first method, you'll need to design and build a sturdy, spring-loaded device that can hold a bat horizontally at the height of the tee. When you pull back on the bat, you apply tension to the spring(s). When the tension is released, the bat swings forward, hitting the ball off the tee. By cocking the bat to the same angle each time, the force of the spring(s) is kept constant for each trial. The main support for the device needs to be firmly anchored to the ground. Exercise proper caution when using the device! Note: if you come up with an inexpensive design that works well, consider helping others by sharing your design with Science Buddies. Contact us at: scibuddy@sciencebuddies.org.
 * 6) For the second method, you swing the bat yourself. Try the following:
 * 7) Do your best to swing the bats at the same speed, regardless of the weight of the bat. Based on what you learned about momentum when doing your background research, what do you expect the results will be? What actually happened? Were you surprised? Why or why not?
 * 8) Swing hard. Do you feel like you are swinging the lighter bats faster than the unaltered wooden bat? What do you expect the results will be this time? What actually happened? Were you surprised? Why or why not?

Design an experiment to investigate the effects of one or more of these methods on hitting distance. Credits Andrew Olson, Ph.D., Science Buddies Sources This project is based on:
 * Can you think of a way to measure your bat speed in order to calculate the momentum of the different bats when they hit the ball?
 * Compare the peformance of aluminum vs. wooden bats of the same weight.
 * Compare peformance of end-weighted vs. normally-weighted aluminum bats.
 * There are other ways to alter the effective mass of the bat, all of them legal under Major League Baseball rules:
 * holding the bat further up the handle ("choking up") reduces the effective length of the bat,
 * cutting the end of the bat off to make it shorter,
 * turning down the diameter of the bat on a lathe.
 * For more science project ideas in this area of science, see [|Sports Science Project Ideas].
 * Glaser, J.B., 2004. "The Physics of Cheating in Baseball," California State Science Fair Abstract [accessed November 6, 2006] [], and
 * Jacobs, A.J., 2004. "The Physics and 'Physiques' of Baseball," California State Science Fair Abstract [accessed November 6, 2006] [].


 * 1) **A corked bat has (slightly) less mass.** By drilling out the center of a wood bat and replacing it with cork a player can shave about 1.5 ounces off of the weight of his bat. More importantly, the location of the center-of-mass of the bat would shift slightly towards the handle end of the bat. This means that the moment of inertia of the bat would decrease and it would be easier to swing.
 * 2) **Less mass (lower inertia) means faster swing speed.** A bat which has less mass, and especially which has a lower moment of inertia, may be swung faster. 1.5oz may not do much for an amateur player, but for a professional it means being able to watch the ball travel an additional 5-6 feet before having to commit to a swing. Plus, research has shown that faster bat swing speed results in faster batted-ball speed, though the change in ball speed would be minimal for most players. The moment of inertia could also be effectively lowered by choking up on the bat, by using a shorter bat, or by shaving some wood off of the handle, all of which are legal methods of reducing bat mass.
 * 3) **Less mass means a less effective collision.** Lowering the mass (and moment-of-inertia) may increase the bat swing speed, but the lower mass means that the collision between bat and ball is less effective. If the swing speed is kept constant, a heavier bat will always propel the ball faster and farther. So removing mass from the bat will actually reduce the batted-ball speed.
 * 4) **No scientific advantage?** Reducing the mass (lowering the moment-of-inertia) increases the swing speed - which increases batted-ball speed. But at the same time the lower mass reduces the effectiveness of the collision - which decreases the batted-ball speed. Which effect is greater is a toss-up. But since the two effects offset eachother, there appears to be absolutely no scientific advantage to using a corked bat - at least for hitting home runs. There would be an advantage to just making contact, however. Because the bat is lighter and can be swung faster, a player can wait a few milleseconds longer before commiting to a swing. This means he can watch the pitched ball travel about 5 or 6 more feet before deciding to swing. For a slumping player this may help make contact with the ball more often. But, a corked bat will not make the ball go faster or further.
 * 5) **Psychological Advantage?** I read a quote by a major league player in one of newspaper reports covering the Sammy Sosa incident that went something like: "I don't care what all those MIT professors say, if players didn't //**think**// it made a difference, why have they been doing it for all these hundreds of years?" Baseball is a very superstitious sport - look at all of the rituals batters and pitchers go through before and during a game. Some players have lucky socks, shirts, hats which they refuse to wash for fear it might ruin their current streak. Other players have a set ritual before each game or each at-bat. The key factor to the corked bat would seem to be that if a player thinks it will make a difference in his game, then it very likely might make a difference. The effect is psychological, not a result of increased performance from the bat itself. Detroit Tigers' Norm Cash admitted to using a corked bat in 1961 when he won the batting title with a .361 average, but the next year he slumped to .243 with the same corked bat.
 * 6) **Why use cork?** Well, the hollowed out portion of the bat needs to be filled with something or the bat would sound significantly different than a solid bat, giving away the illegal modification. Graig Nettles was playing for the New York Yankees in 1974 when he broke a bat during a game and six superballs bounced out. I read somewhere that several Anaheim Angels players had experimented with liquid mercury - which would be very interesting because the moment of inertia would change while the bat is being swung, with the largest inertia just before impact.

Corking a bat the traditional way is a relatively easy thing to do.[2] You just drill a hole in the end of the bat, about 1-inch in diameter, and about 10-inches deep. You fill the hole with cork, superballs, or styrofoam - if you leave the hole empty the bat sounds quite different, enough to give you away. Then you glue a wooden plug, like a 1-inch dowel, in to the end. Finally you sand the end to cover the evidence. Some soures suggest smearing a bit of glue on the end of the bat and sprinkling sawdust over it so help camouflage the work you have done. A couple of years ago Fallon and Sherwood[3] at the UMass-Lowell Baseball Research Center did some experiments with aluminum bats and corked wood bats. They used the Baum Hitting Machine to swing a bat at approximately 66 mph towards a ball moving at 70 mph. After normalizing for inertia properties of the bats they found that corked bats produced batted-ball speeds about 0.9 mph higher than normal wood bats. They also found that their corked bats cracked after as few as 3 impacts, so the data they were able to collect was limited before the bats were damaged. However, their results appear to contradict the basic physics arguments given above.
 * Sammy's corked bat was different.** What makes Sammy Sosa's corked bat interesting is that it was not corked in the usual way, by drilling a hole in the end of the barrel. The cork-filled hole in Sammy's bat was in the taper region at the middle of the bat. This would have a different effect than has been described above. Instead of lowering the moment of inertia by removing mass from the end of the bat, Sosa's corked bat would probably have had a very similar moment of inertia (perhaps even a little higher) than an uncorked bat of exactly the same dimensions. If the taper region was weakened then the bat might be more likely to flex during the swing, a feature which is currently being designed into some of the newest aluminum and composite baseball and softball bats. If the bat flexes during the swing, and if a player can time the swing just right, then the tip of the bat is moving faster than a rigid bat would be when it meets the ball. For a wood bat, the bat speed just prior to the collision is the single most important factor in how fast the ball comes off the bat. So, it is conceivable that Sosa's specially corked bat could give him a slight advantage for hitting the ball faster and farther. Sammy consistently claimed that he used this corked bat occasionally in batting practice to put on a homerun show for the fans. However, as he found out to his embarrassment, using such a bat in a game situation is not a good idea. In batting practice the hitter is hitting balls which are pitched so that he can hit them, in order to help him warm up his swing mechanics. In a game when the opposing pitcher is purposefully trying to jam the batter with a pitch to the inside, a bat which has been weakened at the taper/handle region will break very easily.

An unpublished experiment carried out by Alan Nathan[4] using the same equipment at the UMass-Lowell Baseball Research Center found a very different result. This experiment took two identical wood bats (same length, mass, MOI, etc.) and drilled a 7/8" diameter 9-1/4" deep hole in one of them. He measured the bat-ball coefficient-of-restitution (BBCOR, defined below) of the bat-ball collision and found that the results were //identical// for the normal and corked bats. Using this information and data on how the swing speed depends on the bat's inertia properties from the Crisco-Greenwald batting cage study[5] Dr. Nathan predicted that the final batted ball speed would actually be lower for the corked bat than it would be for the normal bat.
 * ~ Bat ||~ BBCOR ||
 * normal || 0.445±.005 ||
 * corked || 0.444±.005 ||

My Experimental Evidence
After the collision the ball rebounded backwards and the bat rotated about its pivot. The ratio of ball speeeds (outgoing / incoming) is termed the collision efficiency, //eA//. A kinematic factor //k//, which is essencially the effective mass of the bat, is defined as //k// = //mball z2 / Ibat// where //Ibat// is the moment-of-inertia of the bat as measured about the pivot point on the handle, and //z// is the distance from the pivot point where the ball hits the bat. Once the kinematic factor //k// has been determined and the collision efficiency //eA// has been measured, the BBCOR is calculated from BBCOR = //eA(1 + k) + k// The data at right[8] shows a typical result for one of the bats. The plot indicates that the BBCOR is lowest for the drilled (hollow) bat. The BBCOR value for the corked bat is slightly lower than the original bat, though given the error in the measurements the results are basically indistinguishable. This result confirms the previous experiment by Alan Nathan[4] that a corked bat does not have a trampoline effect. || //**Fig. 2.** BBCOR values measured for a normal wood bat and for the same bat after being drilled and corked.// || BBS = //eA vball// + (1 + //eA//) //vbat// where //vball// is the incoming ball speed, //vbat// is the bat swing speed just before collision and //eA// is the collision efficiency (ratio of ball rebound speed to incoming speed). The bat swing speed depends on the moment-of-inertia of the bat.[10] Using the measurements of //eA// along with the bat kinematic factor //k// and knowledge of how swing speed is related to bat moment-of-inertia we obtained the BBS values shown in Fig. 3 at the right. This result suggests that corked bat would produce batted-ball speeds about 1 mph lower than a normal wood bat. || //**Fig. 3.** Batted-Ball Speeds predicted for a normal wood bat and for the same bat after being drilled and corked.// || //**Fig. 4.** Mass-spring model of the trampoline effect showing how hoop frequency predicts performance// || Instructions
 * In July of 2003, I had the opportunity, with [|Alan Nathan] (Univ. of Illinois) and [|Lloyd Smith] (Washington State Univ.), to measure the Bat-Ball Coefficient-of-Restitution (BBCOR) of several corked and normal wood bats. We obtained three professional grade wood bats (33") from Rawlings and measured the BBCOR for all three. We drilled a 1" diameter, 10" deep hole in the end of two of them, and measured the BBCOR of the drilled (but empty) bats. Finally we filled the bats with cork and remeasured the BBCOR. The Bat-Ball Coefficient-of-Restitution (BBCOR) depends primarily on the elastic properties of the ball and bat, with a slight dependence on the moment of inertia of the bat. If a hollowed-out, corked wood bat has a trampoline effect, then it would show up as an increase in the BBCOR. In our experiment, the BBCOR was measured by firing a ball (upwards of 110 mph) from a cannon towards a stationary bat and measuring the speed of the ball before and after it hit the bat.[6] The bat was gripped at the handle by a clamp device which was free to rotate about a pivot, though the bat was initially at rest. For those concerned that clamping the bat in a pivot is not the same as a player holding or swinging the bat, Keith Keonig (Univ. Mississippi) has convincingly shown that batted ball speed is completely independent of the method by which the ball is gripped at the handle.[7]
 * Perhaps it would be even better to compare Batted-Ball Speed (BBS). Batted-Ball Speed may be predicted[9] from
 * One of my meager contributions to the understanding of how a baseball bat works is a correlation between the frequency of vibrations in the barrel of a hollow aluminum or composite bat and its measured performance.[11] A lower frequency of the fundamental hoop mode of the barrel means a softer spring constant of the bat, and a greater trampoline effect resulting in higher batted ball speed. A simple mass-spring model of the trampoline effect yields a very interesting result, indicated by the solid black curve in the figure at right. As the frequency of the hoop mode decreases, the performance of the bat increases until an optimal frequency is reached. Below this optimum frequency the performance quickly falls off. The success of this simple model is evidenced by the general characteristics of baseball bats. The majority of aluminum bats currently on the market have hoop frequencies in the neighborhood of 2000 Hz. The highest performing bat I have seen so far has a hoop frequency of about 1600 Hz. A prototype all-composite baseball bat I had the chance to test in my lab was found to have a hoop frequency of about 1450 Hz. This bat was field tested by a top college baseball team and almost every player on the team was hitting balls in excess of 500 ft. In constrast, a 1989 graphite bat - which was marketed as having the strength of aluminum and the perfromance of wood - has a hoop frequency of 3350 Hz. It did not last long on the market because it was a very poor performing bat, nowhere near the performance of available metal bats. When I measured the hoop frequency of the corked wood bats used in our 2003 study I found the hoop frequency to be in excess of 5300 Hz, which essentially means that any enhancement in performance would be almost negligible. || [[image:images/plot-2.gif]]

Things You'll Need:
Drill hole 1/2-inch-1-inch deep in diameter through top of the wooden baseball bat. The hole should be 6 inches deep minimum, 10 inches maximum. Remove excess wood from drilled hole. Fill hole with crushed cork, sawdust or super balls but leave it unfilled 2 inches from the top of the bat to make room for the wood plug. Insert and glue a wood plug into remaining space in the drilled hole. Sand the top area of bat down to mask wood plug, then apply wood stain, pine tar or other dark matter to cover evidence of a corked bat.
 * Wooden baseball bat
 * Crushed cork
 * Sawdust
 * Glue
 * Superball
 * Wood plug
 * Sand paper
 * Wood stain
 * Pine tar
 * 1) Step 1
 * 1) Step 2
 * 1) Step 3
 * 1) Step 4
 * 1) Step 5

Inertia is proportional to mass. It is a measure of the resistance to changes in velocity. Momentum = mass x velocity

momentum: an impelling force or strength Inertia: a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force
 * b** **:** an analogous property of other physical quantities