Question

[Grade 12 Physics: Experiment in Phyiscs] A question about sources of error - Help!

You want to calculate the area of a specific paper. Discuss in detail the following points:

• Which measuring instrument you use

• How to do the calculation

• Accuracy

• Source of errors

Give a concrete example.

My answer:

I would use a ruler to measure both the base and the height of the paper as the ruler shows millimeters and centimeters and is a suitable tool for measuring short lengths and we can also use the ruler to calculate the area, i.e. the base multiplied by the height. An advantage of calculating the length of the paper with a ruler is because the ruler shows millimeters and centimeters so if we want to be extra accurate with the measurement we can also specify the millimeters in our result, so 19.6cm shows that we have 19cm and 6mm which together gives us 19.6cm. 1mm = 0.1cm. Thus, a ruler with an accuracy of 1 mm can be used.
The base b and the height h are measured and the area is calculated with A = b * h.
It is also important that the paper is seen as a rectangle and that the base and height of this paper are really measured. The ruler should be read straight from the top so that the correct dimensions are obtained.
e.g.:
b = 213 mm, h = 298 mm gives us the area that we wanted.
A = 63474 mm^2 = 635 cm^2.
Sources of error could be calculated by estimating the max and min area:
Max: 214 * 299 = 63986 mm^2 <= 640 cm^2
Min: 212 * 297 = 62964 mm^2 => 630 cm^2
The answer will then be 635 +- 5cm^2.
Sources of error may be that we cannot know with 100% certainty if there is 0.06mm or 0.04mm between every millimeter shown on the ruler, but we can only count on every millimeter that is visible on the ruler, it can also be different on some rulers where you can calculate extra accurately and where there is a new technological ruler that measures lengths digitally and can give correct lengths of objects.
So if we say that the length of the paper is 25.7cm then we do not know for sure whether it is 25.71cm or 25.72cm etc. The paper sheet must not have a rectangular shape with a guarantee.

My teacher said the answer wasn't elaborate enough, and added this:

Examples of sources of error: The ruler does not have the correct scale.

Examples of other sources of error in other labs: ignoring energy losses, air resistance and other effects. Approximations: The sheet of paper does not have a completely rectangular shape.

You should have written more sources of error. The paper may have been crumpled. The ruler may be slightly leaning in the wrong direction when measuring, etc.

What can I add besides what they mentioned and what I mentioned?

Answer 1

I can think of one- . SURAFCE on which paper was placed might not be plain throuhout resulting in error of measurement of length and width.