Stability- The stability of the retort stand could alter the path of the pendulum, the shaking of the retort stand was kept to a minimum as it was held by a group member to keep it stable.
Materials:
Procedure:
*Steps 1-11 were completed before the experiment.
- Four wooden slats were acquired.
- On the first wooden slat 2 cm, 4 cm, 6 cm and 8 cm from the left edge were marked, and 1 cm and 2 cm from the bottom were marked.
- On the second slat 1.5 cm, 2 cm and 3 cm from the right edge were marked, and 1 cm and 2 cm from the bottom were marked.
- Steps 2 and 3 were repeated on the remaining two wooden slats.
- The slats were arranged to obtain the dimensions: 1cm x 2 cm x 6cm
- Chocolate chips were obtained.
- Using a microwave, the chocolate was melted in a microwave safe plastic container at 20-second intervals, stirring occasionally until the chocolate became liquid.
- Using a small spoon the chocolate was poured into the mould created by the wooden slab.
- The chocolate was allowed to cool in the refrigerator until it had solidified.
- Using a straight edge knife any excess chocolate was shaved off so the appropriate dimensions are obtained.
- Steps 5 to 10 were repeated four additional times, with the wooden slabs having the following dimensions instead: 1cm x 3cm x 4cm, 2cm x 2cm x 3cm, 1.5cm x 2cm x 4cm, and 1cm x 1.5cm x 8cm.
- Using an electronic scale, the masses for the chocolate blocks were obtained to ensure the uniformity of mass between each block of chocolate (since the volume of each block of chocolate was the same, the resulting mass should be constant as well).
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String was tied around each block of chocolate making sure that the side facing up (where the knot leading to the pivot is located) is: 2cm x 6cm for the 1cm x 2cm x 6cm block, 2cm x 3cm for the 2cm x 2cm x 3cm block, 1cm x 4cm for the 1cm x 3cm x 4cm block, 1.5cm x 4cm for the 1.5cm x 2cm x 4cm block, and 1cm x 8cm for the 1cm x 1.5cm x 8cm block.
- String measured to 60 cm in length from the centre of the side of the chocolate facing up, was cut using scissors, this was done for all pieces of chocolate (ensure string length is equal).
- Retort stand was set up and ring clamp attached.
- A protractor was attached to the retort stand under the ring clamp (refer to figure 1).
- The piece of chocolate was attached to the ring clamp at the centre of its front end, making sure the distance between the pivot point and the top surface of the chocolate where the string is attached to is 40cm long.
- The pendulum was pulled back at an angle of 40°.
- The timers prepared themselves (in the experiment there were two timers, one measuring the intervals with one period and with five periods, the other timer until the sixth period and the tenth period).
- The pendulum was released.
- The stopwatches were started simultaneously to when the pendulum was released.
- The stop button was pushed after the completion of a full period by one timer, then by the other timer after the completion of 5 periods.
- Steps 18 to 21 were repeated.
- The timer was stopped after the completion of the sixth period by one timer and after the completion of the tenth period by the other timer.
- The results were recorded
- Steps 18 to 25 were repeated 4 more times
- Steps 18 to 26 were repeated for the remaining four chocolate blocks.
Figure 1: Lab setup
Developing a method for collection of data:
For each surface area the resulting periods were measured at 4 different durations (1 period, 5 periods, 6 periods and 10 periods), five times each for increased accuracy as averaged could then be obtained. Averages of the periods will create 5 data points so as to sufficiently demonstrate any trends evident from the data. If more time were available then more tests should be conducted to increase accuracy.
A reproduction of this experiment should yield similar results, however difficulties and discrepancies might arise in finding the same type of string and chocolate. Obtaining the same mass as well as having different reaction times and timing devices may hinder the reproducibility of this experiment.
Data Collection And Processing
Raw Data:
Raw Quantitative Data:
Mass of each piece of chocolate was constant; the pieces were weighed at 18.8g(±0.2g).
*The stopwatches used were different between the 1 period and 5 periods in comparison to the one used for 6 periods and 10 periods, thus the values given varied in the number of figures given (tenths of a second for the first stopwatch and hundredths of a second for the second stopwatch), however due to the general inaccuracy of the testers reaction time the uncertainty will be set at (±0.1s) for all times acquired.
**For the numbered trials it should be noted that the values for 1 period and 10 periods were acquired in a different trial from 6 periods and 5 periods. There are actually ten trials in total, they have been grouped in the following charts for simplicity
Test Bob #1
Dimensions: 1cm x 2cm x 6cm Dimensions of affected sides: 1cm x 6cm and 1cm x 2cm
Chart 1: The time in seconds needed to complete the allotted number of periods.
Test Bob #2
Dimensions: 2cm x 2cm x 3cm Dimensions of affected sides: 2cm x 3cm and 2cm x 2cm
Chart 2: The time in seconds needed to complete the allotted number of periods.
Test Bob #3
Dimensions: 1cm x 3cm x 4cm Dimensions of affected sides: 3cm x 4cm and 1cm x 3cm
Chart 3: The time in seconds needed to complete the allotted number of periods.
Test Bob #4
Dimensions: 1.5cm x 2cm x 4cm Dimensions of affected sides: 1.5cm x 2cm and 2cm x 4cm
Chart 4: The time in seconds needed to complete the allotted number of periods.
Test Bob #5
Dimensions: 1cm x 1.5cm x 8cm Dimensions of affected sides: 1cm x 1.5cm and 1.5cm x 8cm
Chart 5: The time in seconds needed to complete the allotted number of periods.
Raw Qualitative Data:
During the experiment there was no visible difference was noticed between how the different bobs periods were affected by their surface areas. It was noticed however that the paths of motion were not fluid as there was a lot of spinning of the pendulum. The arc that resulted was not a consistent one as there was variation every time due to how the chocolate was spinning and falling.
Data Processing:
Surface area of each bob:
Chart 6: Surface area of all the bobs.
Average time to complete allotted periods:
Test Bob#1: Dimensions: 1cm x 2cm x 6cm
Average for 1 period is 1.1s(±0.5s), 5 period is 6.6s(±0.5s), 6 period is 7.9s(±0.5s), 10 period is 13.6s(±0.5s).
Test Bob#2: Dimensions: 2cm x 2cm x 3cm
Average for 1 period is 1.0s(±0.5s), 5 period is 6.8s(±0.5s), 6 period is 8.3s(±0.5s), 10 period is 13.8s(±0.5s).’
Test Bob#3: Dimensions: 1cm x 3cm x 4cm
Average for 1 period is 1.1s(±0.5s), 5 period is 6.8s(±0.5s), 6 period is 8.1s(±0.5s), 10 period is 13.7s(±0.5s).
Test Bob#4: Dimensions: 1.5cm x 2cm x 4cm
Average for 1 period is 1.1s(±0.5s), 5 period is 6.8s(±0.5s), 6 period is 8.1s(±0.5s), 10 period is 13.7s(±0.5s).
Test Bob#5: Dimensions: 1cm x 1.5cm x 8cm
Average for 1 period is 1.1s(±0.5s), 5 period is 6.7s(±0.5s), 6 period is 8.0s(±0.5s), 10 period is 13.4s(±0.5).
Average time to complete one period through averages of all trials:
Chart 7: The average time taken to complete one period
