Stephen Rueden INT1 Task 3 Sub domain 114.1.1 Scientific Concepts, Theories & Inquiry 4/17/2011

Literature Review: Elasticity and Hooke’s Law: In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform is removed (Elasticity, para. 1). Elasticity was first studied in the late seventeenth century by the English scientist Robert Hooke (1635­1703). He made observations about elasticity using metal springs and eventually developed what is known as Hooke’s Law: The restoring force exerted by an elastic object is proportional to how far it has been distorted from its equilibrium state. Everything we associate with springs, has some place in the behavior of balls (Bloomfield, p.69). When a ball or a spring returns to its equilibrium state, it releases stored energy. Isaac Newton and the Law of Universal Gravitation: Isaac Newton (1643­1727) studied gravity and its effects on falling objects. He is most famous for the three laws of motion. Newton’s law of universal gravitation states that every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The earth’s gravity exerts a downward force on the ball, called the ball’s weight. Its weight causes the ball to accelerate downward (Bloomfield p. 10). Reasoning: What does elastic mean? When a rubber band gets stretched it returns to its original shape. What is something that is not elastic? When a piece of bubble gum gets stretched, it stays stretched. It does not return to its original shape. When a ball hits the floor, the energy of the collision is stored as a physical deformation of the ball (On the Rebound, 2011 para. 3). The ball has kinetic energy just before it touches the floor. As the ball gets squeezed against the floor, kinetic energy is converted to potential energy. If all the elastic potential energy got converted back to kinetic energy, the ball would bounce back to the original height. There is always a portion of that energy that gets absorbed by the ball. That portion of energy is released as sound or heat. The more elastic the material of the ball, (the elasticity of the ball depends on the binding forces of the molecules in the ball) the less amount of energy is released as sound or heat, and the bouncier the ball.

For bounciness, we want to find a number that describes the bounciness (or elasticity) of a ball. We will do this by dropping four different types of balls from three set distances from the floor, and then seeing how high they bounce back.

Image: www.sciencebuddies.com

Hypothesis: To determine what kind of ball is the bounciest between a golf ball, ping­pong ball, racquet ball and a tennis ball due to their elastic potential energy when they hit the ground and see if it is consistent among several different drop heights. The racquetball should be the bounciest because it is the most elastic. Project Design Plan: To test whether racquetballs are bouncier than tennis balls, golf balls and ping­pong balls the rebound heights of all four types of balls needs to be recorded and analyzed. Experimental Design Steps: 1. Drop tennis ball. a. Drop tennis ball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop tennis ball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop tennis ball from 60 cm height two times.

i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. 2. Drop racquetball. a. Drop racquetball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop racquetball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop racquetball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. 3. Drop golf ball. a. Drop golf ball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop golf ball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop golf ball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. 4. Drop ping­pong ball. a. Drop ping­pong ball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet.

iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop ping­pong ball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop ping­pong ball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. Variables: Independent Variable: � Drop Height ­ In this experiment the set of independent variables are the three different drop heights for the four different balls. Drop heights will be measured from the bottom of the ball. Different types of balls used ­ tennis ball, racquetball, golf ball and ping­pong ball.

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Dependent Variable: � Rebound Height – The maximum height of the first bounce for the tennis ball, racquetball, golf ball and ping­pong ball from three different drop heights. Rebound heights will be measured from the bottom of the ball.

Controlled Variables: � Surface on which the ball bounces – Different hardness of floors will cause different absorption of energy when the ball hits the surface causing varying rebound heights for the same drop height. The same ceramic tile floor will be used for all tests.

Threat Reduction to Internal Validity: � The instruments used during testing can change the experiment. If any instrumentation changes occur, the internal validity of the main conclusion is affected (Internal validity, 2011 para. 7). These balls are manufactured to be within certain weight and size tolerances, and may not have identical properties. Therefore, the same tennis ball, racquetball, golf ball and ping­pong ball will be used for all tests to ensure each ball in each test is the same weight and has the same properties.

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Experimenter dropping the balls to ensure that balls hit a horizontal surface of the floor away from grout seams on the tile. On trial runs, it has been observed that the ball would rebound in an upward, horizontal motion instead of an upward perpendicular motion when hitting a seam. To ensure accuracy, each drop is done twice and the two rebound heights are averaged and then recorded. This is due to the limitation of the human eye of the experimenter recording the rebound heights. It is difficult to observe the mark of the rebound height because the ball is there for only a fraction of a second. This is done to reduce parallax errors and random errors. Parallax error ­ Error in reading an instrument employing a scale and pointer because the observer's eye and pointer are not in a line perpendicular to the plane of the scale. Random error – Error in measurement that lead to measurable values being inconsistent.

Appropriate Methods: This experiment will be conducted using quantitative research methods. The data collected will take the form of the mean of measurements and number of drops. These measurements will then be tabulated. Conclusions will be drawn from analysis of the summarized data. The general sequence will be as follows: 1. 2. 3. 4. 5. Observe Tabulate Summarize data Analyze data Draw conclusions

Process of Data Collection / Sequence of Events: One experimenter will be assigned as the dropper, the other will be assigned as the recorder. The experimenters will make three measurements for four different balls. There will be a trial run for each drop, so the experimenters have a general idea where to place the camera. At the end of the experiment, the experimenters will have 12 data points. The experimenters will calculate the median value for each ball. The median value will represent the bounciness value for all four balls tested. A bar graph will be made with the ball type on the x­axis and the rebound height in centimeters on the y­axis.

Tools, Technologies, and Measurement Units: Materials and Equipment: � � � � � � � � � � � One video camera Vertical section of wall and hard flat adjacent floor Three sheets of 36”x24” white card stock to cover wall Clear packing tape Black marker Meter stick Data table and pencil One tennis ball One racquetball One golf ball One ping­pong ball

Measurement Units: � Drop heights are to be recorded in centimeters (cm)

Preparing Test Wall: � � Results: The following observations were made from the ball drop experiment: � � � As the drop height was reduced, the rebound height was also reduced. As the drop height was reduced, the sound heard when it hit the floor was also reduced. As the drop height was reduced, the rebound height to drop ratio increased for each type of ball. This may be due to less energy loss as sound when the ball hit the floor. Tape card stock to the wall until an area of about 6 feet high and 2’ wide is covered. Using the meter stick and the marker, mark and label every inch of paper from the floor up to a height of 140 cm.

The tables below show raw data collected for each ball:

Rebound Height Data Table: Tennis Ball
Drop Height (cm) 140 100 60 Trial 1 Rebound Height 82 66 42 Trial 2 Rebound Height 87 66 42 Average of Rebound Heights 84.5 66 42 Average Rebound Height to Drop Height Ratio .60 .66 .70

Rebound Height Data Table: Racquetball
Drop Height (cm) 140 100 60 Trial 1 Rebound Height 104 77 47 Trial 2 Rebound Height 103 76 46 Average of Rebound Heights 103.5 76.5 46.5 Average Rebound Height to Drop Height Ratio .74 .77 .78

Rebound Height Data Table: Golf Ball
Drop Height (cm) 140 100 60 Trial 1 Rebound Height 81 66 41 Trial 2 Rebound Height 83 63 39 Average of Rebound Heights 82 64.5 40 Average Rebound Height to Drop Height Ratio .59 .65 .67

Rebound Height Data Table: Ping­pong Ball
Drop Height (cm) 140 100 60 Trial 1 Rebound Height 86 61 42 Trial 2 Rebound Height 82 61 43 Average of Rebound Heights 84 61 42.5 Average Rebound Height to Drop Height Ratio .60 .61 .71

The graph below shows the average rebound heights collected for each ball at the 140 cm drop height:

Conclusion: There are basically two possible outcomes. Either the experiment supported the hypothesis and can be regarded as true, or the experiment disproved the hypothesis as false (The Scientific Method para. 1). Data collected from the ball drop experiment demonstrated that the racquetball has a higher rebound than the other less elastic balls. The hypothesis is true. Confirmation of Hypothesis: The experiment conducted to determine what kind of ball is the bounciest between a golf ball, ping­pong ball, racquet ball and a tennis ball due to their elastic potential energy when they hit the ground has proven that the racquetball is bounciest and therefore has the most elastic potential energy. The racquetball was shown to be bouncier from every drop height tested. The analyzed data from this experiment supports the hypothesis. Experimental Design as Key Factor: An Experimental Design is the laying out of a detailed experimental plan in advance of doing the experiment. Well­chosen experimental designs maximize the amount of "information" that can be obtained for a given amount of experimental effort (Experimental Design para 2). In this experiment, two independent variables were changed, the drop heights of the balls and the types of balls used in order to observe the effect or lack of effect of the variables. The data was collected on a data table and then analyzed to yield valid and objective conclusions.

Evaluation of Validity: With the use of this test design, accurate rebound heights for the four different types of balls were obtained. A vertical surface adjacent to a hard floor was used and great care was taken to make sure the measurements fixed to the vertical wall were accurate. The vertical measurements were on a white background and the test area was brightly lit to better capture the images of the bouncing ball. This test design measured what it was designed to measure. Replication: Considerable confidence is added if an experiment is replicated by other researchers. This helps confirm that the previous results weren't dependent on some unreported aspect of the first experiment and that it wasn't the result of a statistical fluke or sloppy or fraudulent work (Replication para. 1). Materials and Equipment: � � � � � � � � � � � One video camera Vertical section of wall and hard flat adjacent floor Three sheets of 36”x24” white card stock to cover wall Clear packing tape Black marker Meter stick Data table and pencil One tennis ball One racquetball One golf ball One ping­pong ball

Measurement Units: � Drop heights are to be recorded in centimeters (cm)

Preparing Test Wall: � � Tape card stock to the wall until an area of about 6 feet high and 2’ wide is covered. Using the meter stick and the marker, mark and label every inch of paper from the floor up to a height of 140 cm.

Data Collection: 1. Drop tennis ball.

a. Drop tennis ball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop tennis ball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop tennis ball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. 2. Drop racquetball. a. Drop racquetball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop racquetball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop racquetball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. 3. Drop golf ball. a. Drop golf ball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop golf ball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet.

iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop golf ball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. 4. Drop ping­pong ball. a. Drop ping­pong ball from 140 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. b. Drop ping­pong ball from 100 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet. c. Drop ping­pong ball from 60 cm height two times. i. Trial 1 note rebound height on data sheet. ii. Trial 2 note rebound height on data sheet. iii. Enter the average rebound heights of trials 1 and 2 on data sheet. iv. Enter the average rebound height to drop height ratio on data sheet.

Works Cited: (2011) Elasticity (physics) Retrieved April 20, 2011 from: http://en.wikipedia.org/wiki/Elasticity_(physics) (2007) Experimental Design Retrieved April 22, 2011 from: http://www.nmmu.ac.za/default.asp?id=3530&bhcp=1 (2011) Internal validity Retrieved April 18, 2011 from: http://en.wikipedia.org/wiki/Internal_validity (2011) On the Rebound: The Height Limits and Linerarity of Bouncy Balls Retrieved April 17, 2011 from: http://www.sciencebuddies.org/science­fair­projects/project_ideas/Phys_p071.shtml Robert Korn (2011) Replication of Experiments: Retrieved April 22, 2011 from: http://www.truthpizza.org/science/experim/replicat.htm (2011) The Scientific Method Retrieved April 22, 2011 from:

http://www.brandonbeltz.com/scimeth/conclusion1.htm Louis Bloomfield (2007) How Everything Works: Making Physics Out of the Ordinary. Indianapolis, Indiana: John Wiley & Sons, Inc. Steven Holzner, PhD., Daniel Wohns (2010) Physics Essentials for Dummies. Indianapolis, Indiana: John Wiley & Sons, Inc.

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