Computer Science: Pendulum Introduction: A basic property of pendulums will be studied in this lab as a method of understanding one function of spreadsheets. As you become more familiar with spreadsheets you will start to use them for a wide variety of tasks and will soon wonder how you ever got along without one! In the prelab homework you went through some introductory material for Microsoft Excel 5.0. Before starting this lab we will discuss this homework as a group and try a couple of simple exercises using Excel.

Pendulum: Teacher Notes Download: (Abobe Acrobat Reader required--download free reader) Print the Pendulum Lab.

Equipment: Pendulum apparatus Pendulum weight with line attached Ruler Stopwatch Lab Introduction: The purpose of this lab is to measure the effect on the length of a pendulum on its period. First some definitions: · Length: Distance from the pivot point of the pendulum arm to the center of mass of the pendulum mass. (In this lab you should use the distance from the hook to the middle of the fishing weight. You will be varying this distance by wrapping more of the line around the hook. This will be measured in centimeters.) · Period: Time for the pendulum to swing from one extreme to the other and back. (In this lab you should measure the time for 10 swings and then divide by ten otherwise you will only be measuring your reaction time! This will be measured in seconds.) Working in a group you need to measure the period for a pendulum at 6 different lengths. Everyone will need to record the results for the second part of the lab. Therefore, everyone should first prepare a data summary file using Microsoft Excel. Data Collection Preparation: Prepare a spreadsheet for input of measurements. You may use the form shown in the sample sheet attached or you may design your own. Make sure that you are able to record the length of the pendulum and three periods for each length. You also need to calculate the average of each set of three periods. The Lab: Gather your group together and obtain from the instructors the equipment listed above. Adjust the length of your pendulum by wrapping the free end of the line around the cup hook. You will run the experiment for 6 different lengths. Try for lengths of approximately 25 cm, 21 cm, 18 cm, 14 cm, 10 cm, and 6 cm. Remember to record the exact length of your pendulum in centimeters to the accuracy of your ruler. Measure the period by releasing the weight at some angle and timing the oscillations for 10 complete cycles. Verify for yourself that the period is independent of release angle. Each person in the group should enter the results in her spreadsheet. Remember to: Enter your exact length and not the approximate length you were aiming at. Enter the length in centimeters and not inches. Enter your time for a period in seconds and not minutes. Divide your time for 10 periods by 10 to obtain the time for one period. Compute the average of the three period measurements for each length. (Use the AVERAGE function in Excel). Plot the period in seconds (x axis) versus the pendulum length in centimeters (y axis) using Cricket Graph. Fit the points to a second order polynomial (quadratic function). Now that you have a equation giving the relationship between period and length, use it to find what pendulum length will give you a period of 0.75 seconds?______________ Analysis: The period (T) of a pendulum is related to the length (L) by the formula: Substituting the constant in and rearranging the equation we get a quadratic equation for the relationship between length (cm) and period (sec): How does this compare with what you determined in step 6 above?