The Hit
Coefficient of Restitution (COR) Exploration

Bat Type Activity
Bat Length Activity
Coefficient of Restitution (COR) Exploration
Graphing Calculator Activity

Overview of Lesson/Goal

This activity is designed to explore the different COR values for three different types of balls (baseball, golf ball and Superball).

Enrichment

Students will observe how temperature changes affect the COR of each ball.

Objectives

• The students will describe the concept of COR.

• The students will conduct an experiment by collecting data to determine COR values of various types of balls.

• The students will plot graphs of COR values and determine which ball has the best elastic properties.

Ohio Academic Content Standards

Materials

• Baseball, golf ball, Superball

• Meter stick

• Graphing paper (or graphing software)

• Calculator

• Ruler

Procedure

1. Keep each ball at room temperature for 24 hours prior to this lab.

2. Have students work in pairs and drop each ball from an initial height of 0.25 meters. Have one student record this value in a data table. See Appendix D for data sheet.

3. Have the other student mark the rebound height of the ball and record this value in the data table.

4. Students should repeat this procedure for each ball for the following initial heights: 0.50, 0.75 and 1.00 meters.

5. Ask students to calculate the square root of each initial height and each rebound height and record these values in their data tables.

6. Have students plot a graph of the square root of rebound versus square root of initial height. (Dependent variable or the square root of the height of the rebound should be graphed on the y axis.) They should do this for each type of ball dropped.

7. Students should then draw a line of best fit through their data points and determine the slope of the line for each graph. Have them show all work.

8. This slope of the line value is their average COR for each ball. Have the students compare these values and answer the analysis questions below.

Enrichment
Repeat this experiment after placing the balls in a freezer for a 24-hour period.

Important Terms for This Activity

• Gravitational Potential Energy (GPE)
• Kinetic Energy (KE)
• Coefficient of Restitution (COR)
• Initial Height
• Rebound Height

Important Equations for This Activity

• GPE = mgh
• KE = 1/2mv²
• COR = v'/v = sqrt(h'/h)

Data Tables

See Appendix D for Student Sheet.

Analysis Questions

1. Based on your data/graphs, which type of ball had the highest COR?

2. In terms of energy, what would it mean to have a ball with a COR of 1.00?

3. Which type of ball would you be able to hit the furthest? Explain why.

Enrichment

1. What effect did lowering the temperature of the balls have on their COR?

2. Would major league baseball players be able to gain any hitting advantages by playing a game on a hot summer day rather than an extremely cold day?

Evaluation

This activity can be evaluated using informal observations as students work together to perform the tasks. This is also an activity in which a formal evaluation can be registered by assessing the students on their ability to accurately collect data, plot graphs, and reach conclusions. See Appendix B for a rubric to evaluate the graph.