- These are the anomalies that I’ve pointed out from the previous table.
The uncertainties:
Changes in uncertainty after they are calculated:
- There is an anomaly in this data, because for the average for marble 5 and 6 there is a lot different compare to the overage that is calculated out from all six marbles. One has +0.08 compared to the average and another has -0.07.
Diameter using Micrometer method
Measured in mm (*10-3m)
- The marble 2 that is measured by a micrometer, I think that the measurement is abnormally perfect. I think that it should not be absolutely the same even though I repeated it for 5 times.
The uncertainties:
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The one with micrometer is not shown on the marble 1 scale, and the reason is because of that they both have the same number, so they overlapped each other. And as well as the fourth one.
- From the graph we can see that from all six marbles, only two of them have the closest or same sized when measuring with string and micrometer, this shows that most of the marbles have different size.
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Marble 5 has the biggest difference. 1.72 (*10-2m) with ruler and 1.62 (*10-2m) with micrometer, the difference between it 0.11 (*10-2m).
As you can see on this graph, I converted the micrometer’s unit into cm, to be able to graph it fairly and to see the differences.
Differences between measuring with String and Micrometer
- For the one that is highlighted, it was not suppose to be the same, but because I round it up so it will be easier to be compared, that is the reason why it became the same. But originally it was only 0.001 different.
- The pink highlighted one has the biggest gap compared to others. And it is shown obviously on the graph as well. And the smallest difference that we have got is zero, which we have it for marble 1 and marble 4. But this does not mean that they are exactly the same, because numbers are rounded up in the calculation, so there is a little different inside them.
To find the volume of the each marble, I used this equation:
This means that for the diameter results above, we will need to divide them by 2 to get the radius, so we can be able to use the equation above. And also for the micrometer, the unit will need to be converted into cm, because the volume is in cm2..
Volume of Marbles from using Micrometer and String
The uncertainties For using String:
- Even though we calculated the volume, marble number 5 that is measured by string still has the highest number out of all of the others.
The uncertainties for using Micrometer:
- This data also proves that, by using the micrometer there is less differences compared to the average.
Example Calculation/Checking for String:
Checking for Micrometer:
Conclusion:
From my investigation I found out, when I measured with strings and then measured with micrometer, there isn’t much difference, but there are some do have differences. From the graph on the diameter it shows that for marble 1 and marble 4 it has the same results in measuring with string and micrometer, and this is not what I expected, because in my prediction I thought every measurement for strings and micrometer would be different.
Furthermore, I’ve found out that machine made marbles are not an exact same size. And machine made marbles can vary as much as 1/16 inches diameter depending on the manufacture, since it is made in a mold, so none of them will be exactly the same. In addition, machine made marbles are made through many processes, such as for the glass marbles that we measured, they were made by one of the mechanical technique which is dropping globules of molten glass into a groove that is made by 2 interlocking parallel screws, and then as the screws rotates the marbles travel along them and gradually being shaped into a sphere as it cools.
I think that the process of the marble creations can cause the size of each marble to be different, because the dropping of globules might not be all the same amount, and the groove might be not all in the exact size, and since it is a cheap product, its manufacture does not need to be the same. Also, marbles are just using for playing or decorating, so it is not that significant to make them all the same.
I’ve also discovered that if I measured a marble in different direction in micrometer or strings it gives me different measurements. I think this might be due to the surface of the marble, from our eye sight it might looked like it is actually circular, but actually it might not be circular, because it is a circle, no matter which direction I used to measure, they will all be the same.
Looking at the raw data, I’ve found some important points to show the differences in using string and micrometer:
In the marble 3, 5 and 6 the repetitive experiment they are quite different, as I highlighted on the data above, the highest and the lowest measurements has a big different compare to using micrometer:
As you can see with the micrometer it only shows a little different, it I convert this into centimeter, everything will be 1.6…cm, compared to by using the string, it goes in a range or 1.4 to 2.04cm.
From this experiment, I’ve learned that it is more accurate to measure with micrometer than string, because marbles are small which their unit would be more accurate to measure in millimeter than in centimeter. And for micrometer, I think since we are comparing the diameter, using micrometer would be more appropriate, because by using micrometer we can measure the diameter straight ahead, and it stays still.
Some things that I have learned are that, the uncertainty of maximum and minimum changes throughout the calculation, for both string and Micrometer method. In the beginning, it was all ±0.05, but then as we divide it by π from the circumference to get the diameter the uncertainty changed to ±0.02, and then when I divided by 2 to get the radius the uncertainty dropped to ±0.01 and for the volume, it dropped all the way down to ±0.1.
Evaluation:
The weaknesses from the experiment would be due to the limited equipments that are available in the physics room. Such as that, using strings to measure marbles are not that appropriate, because it slipped a lot, as well as using the school ruler, because ruler that we were using shows 0.1cm between each scale, but it would have been better if there is a ruler that shows smaller number between it.
Also the marbles that we have used in the physics room are used for a long time, because many of them were chipped or has crack on them, which I think it might affect the measurement because the surface is damaged. This shows that, if I could redo my experiment, I would buy a new marble, so the surface of the marbles is all the same. In addition, rather than complaining about this, I think I could have used 3 different kinds of ruler to measure the strings, as well as I could have look at the brand new marbles to see how the new ones are different from the used ones.
For some of the improvements on my lab if I could do it again, will be that I would use more devices to measure the size of marbles if there are other available equipments. And for the further investigation, I would try measure handmade marbles (if I can find it), and compare it with the machine made marbles, to see whether handmade marbles are all in the same size of is it the same as machine marbles, that all the sizes are different.
And the most important thing was that, I think if I could do it again, I would change the uncertainty for the micrometer, because if the uncertainty for ruler is ±0.05 and it wouldn’t be the same for the micrometer, it should have been smaller than that, so I think I might have made a mistake in the lap, but at the end I still got the result that I was expected.