SECTION 1: EXPERIMENT AND OBSERVATION

Transcription

1 SECTION 1: EXPERIMENT AND OBSERVATION A. ABSTRACT This experiment was to build a homemade pendulum which was used to measure gravity s acceleration while in swinging back and forth while anchored to a stable object. This experiment was evaluated, documented and graphed to the best of my knowledge. B. MATERIALS / EQUIPTMENT LIST Towel Rack (used for support) Digital Scale 500 g Pen (for note taking) Calculator Scotch Tape Press n Seal (used as a bag) Computer and Microsoft Office Excel 2007 Program Labpaq Spring Scale 500 g (did not use) Measuring Tape, 3 meters iphone (as a stopwatch instead of the the digital stopwatch shown in Photo 1) Protractor 12 Steel Washers (~ 4.3 g each) String 4 m Photo 1 - Lab 7 Materials Page 1 of 6

2 C. DATA (Tables and Images) Data Table 1 String Length = 100 cm = 1.0 m Bob (Washers) Mass = 26.0 g = kg Pendulum (1 meter) with Bob (26 grams) Timed (5 periods) Trials Amplitude ( ) Amplitude (cm) 1 st Trial 2 nd Trial 3 rd Trial Average Time 5 cycles each Period 1 cycle Gravity s Acceleration (m/s 2 ) Data Table 2 Bob (Washers) Mass = 26 g = kg Amplitude = 25 Varied Length Pendulum Timed (5 period) Trials Length of String (m) 1 st Trial 2 nd Trial 3 rd Trial Average Time 5 cycles each Period 1 cycle Gravity s Acceleration (m/s 2 ) Data Table 3 String Length = 100 cm = 1.0 m Amplitude = 25 Weight of Bob (g) 1 st Trial Double Weighted Pendulum Timed (5 period) Trials 2 nd Trial 3 rd Average Trial Time 5 cycles each Period 1 cycle Gravity s Acceleration (m/s 2 ) Page 2 of 6

3 Photo 2 - Lab 7, Homemade Pendulum (the 26 gram bob is circled in red) SECTION 2: ANALYSIS A. CALCULATIONS 1. All gram measurements were converted to kilogram measurements for calculating force. (Example: 4.25 g = kg) 2. The average mass for the steel washers was calculated by taking the total weight of 6 washers and dividing the weight by the number of washers. (Example: 26 g / 6 washers = 4.33 g) 3. 5 cycles of time were recorded in seconds and then divided by 5 to acquire an average of 1 cycle. (Example: 10 seconds / 5 = 2.0 seconds) 4. The average time was calculated by taking each trial time and dividing it by the number of trials. (Example: (9.8 * 9.1* 9.7)/3 = 9.53 s) 5. From all three Data Tables listed above, gravity s acceleration was calculated by the following equation: g (gravity) = [(2pi) 2 * L (length)] / t 2 (time). (Example: ((2 * Π)2 * 1 meter) / 1.94 s) = m/s 2 ) Page 3 of 6

4 B. GRAPHS Please see Error Analysis section of this Lab Report for graphs. The graphs closely relate to the Earth s gravitational attraction of 9.8 m/s 2. C. ERROR ANALYSIS Chart 1 The above scatter plot displays the varied degrees of amplitude versus gravity s acceleration. The green points represent the pendulum s bob with a weight of 26 grams and the purple square represents the pendulum s bob with a weight of 52 grams. The data recorded is within a reasonable window of accuracy. Chart 2 The above scatter plot displays the varied length of the pendulum versus gravity s acceleration. The data recorded is within a reasonable window of accuracy. Page 4 of 6

5 SECTION 3: DISCUSSION AND CONCLUSIONS A. DISCUSSION 1) According to Data Table 1 and Data Table 2 with the amplitude of 25 degrees, there did not seem to be much change in the frequency and gravity s acceleration. The slight difference could be due to air flow due to less mass. 2) According to Data Table 1, the smaller the amplitude, the larger the resulting period. 3) As the length of the string decreased, the period and frequency decreased according to Data Table 2. 4) If a larger amplitude was used on the pendulum in this experiment, frequency would not change since it is independent of amplitude. 5) If a magnet was placed just under an iron bob pendulum, the time it would take to complete one period would decrease due to the added gravitational pull. 6) The value of g in all three Data Tables was very close to Earth s 9.8 m/s2 sea level calculation. The average times in Data Table 2 were a bit larger due to not having the measuring tape closer to the pendulum so taking an accurate reading was difficult. 7) a. With a pendulum on top of a high mountain, the force of gravity decreases so the period would be longer. b. A pendulum under a weightless setting would stop moving since the force of gravity is what keeps it going. B. RESULTS One end of a string was tied to a towel rack with the other end holding a bag of washers totaling 26 grams in weight. This man-made pendulum was swung back and forth so that each complete cycle could be timed. The average time was computed immediately to verify that no errors have been made. (See Data Table 1). The second set of trials was done by changing the length of the string, with the data recorded in Data Table 2. Press n Seal was used to place another 6 washers along with the 6 already attached to the bob. With the larger mass, the average time still remained the same as the trials taken the first time. (Comparing Data Table 1 and Data Table 3). Page 5 of 6

6 C. RESULTS INTERPRETATION Please see Data Tables 1, 2 and 3 which shows the results and verifies that gravity s acceleration is very close to Earth s 9.8 m/s2 sea level calculation. D. ERRORS: SOURCES AND WHY Data 1 Table has the 30 amplitude trial omitted due to the limited space the pendulum had to swing. The digital stopwatch was abandoned due to severe inaccuracy. The stopwatch application on my iphone was used instead. According to Data Table 2, the average times seemed a bit off. This was due to the length of the string not staying the same because I did not want to cut the string which I believe will be used in future Lab Reports. Page 6 of 6