1. Pendulums… Competency Goal 4: Conduct investigations and use appropriate technologies to build an understanding of forces and motion in technological designs. 4.01 Determine the motion of an object by following and measuring its position over time.

2. Pendulums What effects the swing of a pendulum? Is it: –Amplitude and Frequency –Mass and Frequency –Length and Frequency How can we find out? Let’s make a pendulum and test our ideas.

3. Making your Pendulum Cut a length of string 50 cm long. Open one paperclip into an “S” and tie it on the string. Tape the string to a pencil and then to the side of your desk and add one washer for weight to your “S” clip. Using the tape measure, measure the length of the string from the table top to the bottom of the washer. It should hang down 45 cm. (Roll any extra length onto your pencil.)

4. Continued... To start the pendulum moving bring the washer up even with the desk top (90 )and drop. DO NOT push or thrust the washer forward just drop it.

5. Continued... When counting the swings you must count the forward and back motion as ONE swing. This motion is a cycle. Practice counting with this pendulum. 1 2

6. Continued... Begin your investigation by swinging your pendulum and counting the cycles in a 15 second period. One person must watch the clock for start and stop times. Do this 3 times counting the number of cycles. RECORD each trial number in your journal.

7. Finally… When you have completed your 3 trials find the average. Add the three numbers up and divide by 3. Place your results on the number line. Observe the results. Try the investigation again but use half as much displacement of the pendulum when you swing it. (45 ) Record your results and mark them on the number line.

8. What else to do... Now let’s repeat our experiment and add more weight. Add three more washers to your same pendulum. Predict what will happen. Now try out your new pendulum for 15 seconds three different times and find the average. Place your results on the number line. What are your findings? Did you learn anything?

9. Still more testing Now create another pendulum using a length of string longer than your current one. Let’s use 60cm. Tie the “S” clip on and place two washers on it. Predict what will happen. Displace it 90 and test the results. Continue with three trials and take the average.

10. Continue… Now roll up the string until it is 30cm in length. Again predict what will happen. Continue with three trials and take the average. Place your results on the number line.

11. Conclusion How did the number of cycles per 15 seconds differ when using a pendulum that was longer than the others? Which variable matters the most in determining the number of cycles per 15 seconds? Write a sentence that describes how the length of the pendulum affects its number of cycles per length of time.

12. http://phet.colorado.edu/en/simulation/pendulum-lab Visit the site below for an interactive pendulum that students can adjust and investigate.