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Science Research Project
Physics- Unit 1
High School - Australia
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How are pendulums used in everyday life
and are there factors that affect their
period?
‘
Abstract 3
Abstract
The investigation was to find what factors (mass, angle, air resistance and string length ) will increase or decrease the time taken for a pendulum to complete a period (one back and forth swing). Using a retort stand, weights and string were used to create a pendulum so that different factors could be tested by recording the period using a stopwatch timer. Overall the outcome
- Aim
- Hypothesis/Theory
- Introduction
- How are pendulums used in everyday life?
- How does a pendulum work? What are the parts of a pendulum?
- What is the frequency of a pendulum?
- Pendulum Periods
- Variables
- Materials and Equipment
- Risk Assessment
- Method
- Results
- Mass Change
- Angle
- Air Resistance
- String Length
- Evaluation
- Discussion
- Description/Analysis of Results
- Sources of Errors
- Human Timing
- Explanation of Results
- Conclusion
- Bibliography
- Appendix
Pendulum Periods
Period 2 : Is the time it takes the pendulum to make one full back-and-forth swing. Time period 3 : Depends on its length oscillation (regular movement back and forth in a repetitive rhythm).
Variables
Dependent: The time of one period (first swing). Independent: The length of the string, air resistance, the mass of bob and amplitude/angle the bob is released from. The length of the string- Length of the string was a major factor according to many sources explaining that “the longer pendulums swing with a lower frequency than shorter pendulums, and it will have a longer period”. Air resistance- Air resistance was another suggested factor due to drag affecting all movement as air resistance “affects the swing rate because gravity pulls the pendulum down, the pendulum is acted upon by the gravity to cause it to slow down” Mass of bob- Websites suggest that mass doesn’t affect the speed of the pendulum in any way due to “force and mass are proportional and when mass increases so does force and vice versa” Amplitude/angle the bob is released from- The angle was presented by websites to have a slight change in its period however websites mainly suggested it affecting “the swing rate because gravity pulls the pendulum down, the pendulum is acted upon by the gravity to cause it to slow down”. Control: Gravity, same area, the height of the arm the bob is suspended from.
Materials and Equipment
Materials: - 4 x String (15cm, 25cm 4 , 35cm, 45cm) - 7 x Weights (50g each) Equipment: - Protractor - Retort stand - Clamp - Boss head - Stopwatch - Fan - Tape
Risk Assessment
Hazard Risk Management
2 See figure 2. 3 See figure 3. 4 25cm is the constant
The pendulum string/wire breaks and the bob either continues its period and hits someone in their face or drops and lands on someone.
When the pendulum bob hits someone in the face or drops onto someone’s foot
Keep away from the swinging bob when in motion. Wear leather shoes to protect the feet.
Retort stand falls over because the weight is too heavy on the other end. If the weights are uneven because the weight is too heavy and it will cause the retort stand to fall on someone’
When it falls, it may fall on someone’s foot and they may get injured. It could also fall on someone’s face if they are leaning too close.
Ensure that the retort stand is always stable and make sure the weights are similarly balanced.
Safety shoes Weights
Method
- Measure 50cm from the base of the retort stand and place the boss head and clamp there.
- Cut the string into four pieces, 15cm, 25cm, 35cm and 45cm 5.
- Use the 25 cm piece of string and attach 150g weight to the string. Then tie the string onto the arm of the clamp. Attach the weight (bob) to the end of the string.
- Keeping the string straight, raise the string to 50cm high (in line with the clamp) so that it creates a 90-degree angle with the rod.
- Release the string from the height, using a stopwatch to time one period and record the result in the appropriate table.
- Repeat steps 3, 4 and 5 for mass change:
5 Note that when you tie the string to the clamp and the bob you will lose 5 cm in string length.
250g 1 1 1 1.
300g 1 1 1 1.
350g 1 1 1 1.
Angle
Test 1 Test 2 Test 3 Average
(Seconds) 9 (Seconds)
90-degree drop angle (Control)
1 1 1 1.
60-degree drop angle
1 1 1 1.
75-degree drop angle
1 1 1 1.
115-degree drop angle
1 1 1 1.
120-degree drop angle
1 1 1 1.
8 All tests are conducted with 150g of weight, 25 cm of string length and no air resistance. 9 These test results are an average of two stopwatches.
Air Resistance
Test 1 Test 2 Test 3 Average
(Seconds) 11 (Seconds)
No air resistance 1 1 1 1.
Low air resistance (Control)
1 1 1 1.
Medium air resistance
1 0 1 1.
High air resistance
1 1 1 1.
10 All tests are conducted with 150g of weight, 25cm string length and a 90-degree drop angle. 11 These test results are an average of two stopwatches.
Evaluation
The experiment was conducted reliably and validly, however, there were some small errors. One of which involved the retort stand. As it was not completely stable it could have affected the swing of the pendulum and its period.
The wobble was observed to be greater on one side, which caused the pendulum to swing in one direction more, which may have affected the results. This could be prevented by using a completely stable retort stand that does not wobble or shift.
Another issue that was found was the timing may have been inaccurate as using two human timers to record the time taken. Human timers are not always as reliable as their reaction speeds and are not consistent. A way to stop this occurring could be setting up a high-speed camera to capture the exact moment the pendulum reaches the peak of the period and using the length of the video to find the true time
The last issue was that the angle at which it was being dropped may have been different between each test as a protractor was not used each time to check each time. When the angle was measured, human error may have occurred and have caused us to drop the weights at an incorrect angle. A way to fix this could have been to use a protractor for every test as well as
hold the bob with another clamp and retort stand at exactly the right angle.
Discussion
Each of the variables had differing results. The results show that string length had the greatest effect, mass and angle had a small effect and air resistance had no noticeable difference. The results weren’t completely valid with some cases of errors, these errors affected the validity of the experiment. However, the experiment was conducted reliably, with the same test being conducted three times to ensure the reliability.
Description/Analysis of Results
The results display that string length affects the time taken to complete a period, with the longer the string the more time taken for the pendulum to complete its first period. This would have been a direct effect of the formula which involves the radius or length of the string. Other results including mass and angle affected the time taken, but on a smaller scale with a less notable difference. This was due to the force cancelling out the extra mass or angle at which it was being dropped at. Air resistance was the variable that had next to no effect, this was most likely due to the extra air resistance on the first swing being cancelled out by the push given by the fan on the swing back. Since the fan was giving an equal amount of force each time, this meant that there were almost no notable differences in time.
Sources of Errors
The sources of errors vary from human errors, equipment flaws and environmental factors. Major human errors such as human timing and calculation, unreliable angles such as the experimenter’s hand to release the bob and inaccurate measurements have impacted the inaccurate results through its. Additionally, equipment faults such as the retort stand wobbling and consistency of fan movement have affected the results. Environmental factors such as conducting the experiment on different days, inconsistent air resistance and human interruption have impacted the reliability of results.
Human Timing (Human factor)
The major error was the measurement system used. Human stopwatches are unreliable as there is an inaccuracy in timing due to human delays. In compensation for this error, two people were used to record the period and more tests were conducted to have a more reliable result and a increased reliability. This error could have been improved with formulas that measure for all factors or with the availability of more timers and trails this could have a more reliable result. If this improvement was implemented the results will be more accurate and it will be valid however it will still be unreliable due to the other errors such as the environmental factors and equipment issues.
Wobbling Retort Stand (Equipment fault) The wobble of the retort stand was an issue faced in the introduction of experimentation however, this issue could not be resolved but it was reduced. This wobbling caused unreliability as it was an issue that should be controlled so the experimentation was only testing one factor
factors with the experiment. Additionally, air resistance is not a factor as logically the wind pressures towards the bob thus critically affecting the first swing and this carries through towards the backswing which alters where the bob concludes its period.
These results present the reasoning of the uses of everyday applications such as clocks and the understanding of why certain aspects are needed within them. The use of pendulums is to mainly to depict an accurate timing system and to test gravity. However, the most reasonable use for everyday uses of pendulums will be to tell time accurately. Pendulums included within clocks are usually enclosed as air resistance (drag) will affect the timing which makes it inconsistent, which has been depicted in the issues. Also, this cabinet is used to ensure that no other factors such as human interferences can disturb with the accuracy of time. The pendulums within clocks are countered balanced with mass to balance the frequency or period and the reason for the weights is to balance the angles as they have some impact in the period from the conclusion of the results. String length had the largest effect on the time taken to complete the first period with a significant change in results. The results showed the notable difference because of the radius/ string length is directly linked to the time period formula. An example in real life would be a wrecking ball, the smaller the chain, the faster the ball could break through a building. The wrecking ball would be a lot faster if it had a much shorter chain length because the results suggest that the shorter the length, the faster the building can be demolished. Therefore, the results portray the reasoning of how and why pendulums are used and manufactured in a certain fashion.
Conclusion
The aim “To examine factors such as mass, angle, air resistance and string length will affect the period of a pendulum” was explored as string length was the major factor to affecting the period and mass, angle and air resistance did not consistently affect the time of the pendulum period. The hypothesis, “If the factors affecting the pendulums are changed then the period of the pendulum will be increased or decreased. Out of the factors that are being tested, the string will affect the time taken most”, was supported because the hypothesis stated that the factors would affect the time taken for a pendulum to complete its first period, with the length being the most effective. The results display that the factors will affect the time taken for one period but only under the correct conditions.
The results weren’t very valid but show that the heavier the mass of the weight (bob), the period was completed in less time. Another factor used was the change of the drop angle and the results display that the larger the angle, the more time needed for the bob to swing back into place (one period). Air resistance had no real effect on the pendulum’s period as the fan was not substantial enough to make any difference to the period. The change in string length gave the most significant result as the longer the string got, the greater the time taken for the pendulum to complete one period.
Bibliography
Encyclopedia Britannica. (2018). Pendulum | device. [online] Available at: britannica/technology/pendulum [Accessed 29 Aug. 2018].
Evan's Space. (2018). Factors that affect the period T of a pendulum. [online] Available at: google.com/amp/s/evantoh23.wordpress.com/2016/04/04/factors-that-affect-the-period-t- of-a-pendulum/amp/ [Accessed 29 Aug. 2018].
Physicsclassroom. (2018). [online] Available at: physicsclassroom/getattachment/reasoning/waves/src28.pdf [Accessed 29 Aug. 2018].
Sciencenetlinks. (2018). Exploring Pendulums - Science NetLinks. [online] Available at: sciencenetlinks/lessons/exploring-pendulums/ [Accessed 29 Aug. 2018].
Sciencing. (2018). [online] Available at: sciencing/affects-swing-rate-pendulum- 8113160 [Accessed 29 Aug. 2018].
Sciencing. (2018). [online] Available at: sciencing/use-pendulums-real-world- 8417546 [Accessed 29 Aug. 2018].
Figure 4. Photo of experimentation of air resistance affects the pendulum period
Figure 5. Setup of the pendulum with string, weights and retort stand
Science Research Project
Subject: Physics- Unit 1
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