Preliminary (2): Investigating the speed of a chosen ball dropped from different heights
Method
- Fill the measuring cylinder with the viscous liquid (glycerol) until it reaches 250ml.
- Attach the 30cm ruler to the outside of the measuring cylinder using the elastic bands.
- Chose the size and material of the ball.
- Tie the string to the hook of each ball.
- One student should be the timer and the other to drop the ball into the viscous liquid.
- Using the string, hold the ball in the cylinder above the glycerol, aligning it with the brim of the cylinder and the height chosen.
- Make sure that when the ball is dropped that the stopwatch is started as soon as it hits the liquid.
- Stop the watch when the ball reaches the bottom.
- Repeat steps (1) – (7) two more times, but remember to change the height of the dropping every time.
- Work out the mean result.
Preliminary Results (2)
All results to 2 decimal places (2.d.p)
In this preliminary I used a Lead ball with a diameter size of 15mm (millimeters) and dropped into the viscous liquid (glycerol) at different heights (difference of 4 cm every time) to see how it would affect the speed. From the results, the time and speed for each drop is fairly similar even though the balls were dropped from different heights, therefore meaning that these results could be reliable. This preliminary could be suitable to do as there are not too many implications on the results and because the results are consistent which make the experiment reliable.
Preliminary (3): Investigating how the change in the volume of glycerol affects the speed of the ball.
Method
1) Fill the measuring cylinder with the viscous liquid (glycerol) until it reaches 250ml.
2) Attach the 30cm ruler to the outside of the measuring cylinder using the elastic bands.
3) Chose the size and material of the ball.
- Tie the string to the hook of each ball.
- One student should be the timer and the other to drop the ball into the viscous liquid.
- Using the string, hold the ball in the cylinder above the viscous liquid (glycerol), aligning it with the brim of the cylinder.
- Make sure that when the ball is dropped that the stopwatch is started as soon as it hits the liquid.
- Stop the watch when the ball reaches the bottom.
- Repeat steps (1) – (8) three more times, but remember to change the volume of the glycerol.
- Work out the mean result.
Preliminary Results (3)
All results are to 2 decimal places (2.d.p)
In this preliminary, I used a lead ball with a diameter size of 15mm (millimeters) and dropped into the viscous liquid (glycerol) but changing the volume of the viscous liquid every time. In this preliminary the range of the results for the first two tests were fairly similar, however there is and outlier and this suggests that the experiment is quite unreliable due to implications such as the stopwatch not being pressed at the correct time. Another cause of the outlier could be that from the previous test, the glycerol was not wiped off properly and so it affected the speed of the ball.
Conclusion
In preliminary (1) my variable was the different materials of balls and I kept the type of viscous liquid (glycerol) and the same type of ball throughout this preliminary. The ranges of the results in this preliminary for two of the tests were quite similar which suggests that the results are reliable. However it may not be accurate as there were a few implications such as the weight of the lead ball, which was in fact heavier than the brass and copper by about 1000g, which affected its actual average speed. Furthermore, the results of this preliminary may be inaccurate due to as it depended on the students reflexes so the results taken could be inaccurate and unreliable as their reflexes could have changed in each test. This preliminary would not be suitable to do as the results taken would be very inaccurate.
In preliminary (2), my variable was the different types of liquids and I kept constant the Lead ball with a diameter size of 15mm (millimeters). In this preliminary the range of the results were small which alike preliminary (1), suggests that the experiment is quite accurate with few anomalous results. The results were quite consistent which therefore the experiment is quite reliable, having being able to repeat the results. However as there were outliers, it could prove to be unreliable due to implications such as aiming to time and drop the ball simultaneously. Also, the outlier caused in the glycerol experiment could have been caused due to the fact that we only used one ball and after the first result was taken, although we wiped off the glycerol, there could be still some glycerol residue on the ball every time we took a result. This preliminary could be suitable to do as there are not too many implications on the results and because the results are consistent which make the experiment reliable.
In preliminary (3), my variable was the change in height from where the ball was dropped from and I kept the type of ball and the amount of viscous liquid (glycerol) the same. The results this time were very similar and consistent. which suggests that they are accurate and reliable as there were no outliers However this experiment could be unsuitable to do, as the range of the results are so similar, it would be hard to see a real difference between the results. There were also implications as the accuracy of the results could have been affected, since it depended on each person’s reflexes in timing and dropping the ball.
In conclusion, I chose to do preliminary (2) for my main experiment even though the results were very similar, with a small change in method the results should become even more accurate. Also this experiment has little implications on the results and it could be improved to be more representative by specifying the variable.
Main Experiment: Does dropping the ball nearing from different heights affect the time?
Equipment needed: - 250ml measuring cylinder
- String
- Stopwatch
- One chosen ball bearing
- Viscous liquid ~ glycerol
- Cotton thread
- Ruler (30 cm)
- Elastic bands
Method
- Fill the measuring cylinder with viscous liquid (glycerol) until it reaches 250ml.
- Attach the 30cm ruler to the outside of the measuring cylinder using the elastic bands.
- Tie the string to the hook of the chosen ball.
- One student should be the timer and the other to drop the ball into the viscous liquid.
- Using the string, hold the ball in the cylinder above the viscous liquid (glycerol) aligning it with the brim of the cylinder and the height from which the ball is to be dropped from.
- Make sure that when the ball is dropped that the stopwatch is started as soon as it hits the liquid.
- Stop the watch when the ball reaches the bottom.
- Repeat steps (1) – (7) three more times, changing the height every time.
- Work out the mean result.
I chose to repeat the test three more times so I would have four data values, which would make the results much more accurate and reliable.
I also chose to work out the mean for each result to be able to read the data properly, and since it would be the average I would be able to identify any outliers.
Maintaining variables constant
As the main variable is the different in height of each ball dropping, I decided to keep other variables the same, such as the size of the ball bearing, to make it a fair test.
The volume of the liquid is kept constant as any change in the amount of liquid would affect the end result. To make it a fair test, any liquid lost when the ball bearing was removed would be replaced by extra viscous liquid, that way the volume of the liquid was always constant.
The ball is also a constant variable in this experiment and this improves the accuracy of the collected results as it would not be affected by changes due to the use of different balls which could have slight changes in diameter and weight.
Furthermore, to make the results as accurate as possible, we had the same students responsible for the stopwatch and dropping the balls as we were hoping that there would not be a huge change in reflexes.
Experiment Results
All results to 2 decimal places (2.d.p)
