Questions: 1. Name three examples of qualitative observations. Why do qualitative observations tend to be vague? 2. Why are length, mass, and time fundamental quantities? 3. What are the standard (SI) units for length, mass, and time? 4. What are the definitions of accuracy and precision? 5. What is the smallest division of a ruler? 6. What is the precision of the ruler? 11. Why is the ten-oscillation method for measuring the pendulum's period preferred over simply measuring one oscillation? Does this involve accuracy and/or precision? 12. Is there a relationship between the length of a pendulum and its period? How would you describe it? Title: Pendulum Objective: You will investigate a relationship between period and length of a pendulum. Apparatus: string, scotch tape, stop watch, pennies Background Theory: In the pursuit of science, making measurements is an essential tool in observations and experiments. If measurements did not exist, physical quantities could only be described qualitatively, prone to the limitations and potential flaws with human sensory perceptions. Therefore, students in science courses need to learn how to make measurements. Length, mass, and time are three fundamental quantities in the physical sciences. Students need to learn how to measure these quantities accurately and precisely. Often, measurements are recorded in data tables and/or plotted in graphs to help analyze the data gathered during experiments. The precision of each instrument is defined as half the size of the smallest division of the instrument. Measurements made with a meterstick or a ruler should be recorded to the nearest tenth of a millimeter. This requires estimating (i.e. "guessing") the final digit of precision. You will measure period of a pendulum. The period of a pendulum is the time required to complete one oscillation. Is there a relationship between a period and length of a pendulum? Experimental Method: 1. Construct the pendulum using a ruler (with a central hole at one end), string, pennies, and a heavy book. Place the ruler flat on a table with about 20 cm hanging over the table's edge. Place a heavy book on the portion of the ruler that is on the table to keep it from moving. Run the string of the pendulum up through the hole in the meter stick. The initial pendulum length will be exactly 50 cm. The pendulum length is measured from the bottom of the ruler to the middle of the bob. You will use 4 pennies for the bob. Affix the string to the ruler with a piece of scotch tape so that the pendulum length does not change. Place another ruler on the floor, with the 15 cm mark directly under the pendulum bob. This ruler will be used as a reference to measure the pendulum's horizontal displacement. 2. To initiate motion, pull the pendulum back to a horizontal displacement of 10 cm. Use the stop watch to measure the time required to complete one oscillation, which is by definition the period of the pendulum. Record the period in Table 1.1. Time measured using the stopwatch should be recorded to the nearest hundredth of a second. Repeat this process four more times for a total of five trials. Afterwards, calculate the average period. 3. Again, using a horizontal displacement of 10 cm, measure the time required for 10 oscillations. Divide this by 10 to calculate the period. Enter the data in Table 1.2, repeating two more times for a total of three trials. 4. Shorten the pendulum length to 20 cm. Determine the period by using the ten-oscillation method as in the previous step. Record your data in Table 1.3. Afterwards, lengthen the pendulum to 80 cm, and repeat the procedure one last time, entering your data in Table 1.4. Data: Table 1.1 Trial Number #1 #2 #3 #4 #5 Average Table 1.2 Trial Number #1 #2 #3 Average Pendulum Length (cm) XXXXXXXXXXXXXXX Table 1.3 Trial Number Pendulum Length (cm) #1 #2 #3 Average XXXXXXXXXXXXXXX Table 1.4 Trial Number Period (s) Time for Ten Cycles Period (s) (s) Time for Ten Cycles Period (s) (s) Time for Ten Cycles Period (s) Pendulum Length (cm) (s) #1 #2 #3 Average XXXXXXXXXXXXXXX