To investigate the strengths of 3 different threads and which is the strongest we have, we used a clamp stand, 100g and 50g weights and 3 different types of threads. All of the threads we used were the same colour (black). The threads we used were: Rayon (synthetic) cotton (natural) and silk (natural).
We measure the threads (30cm) and tied them to the clamp stand, tying each thread in three knots, and then attached the weights, again using three knots. We then carefully added the weights to see when the threads snapped. We tested each thread seven times to make the test fairer.
Weigh needed to break (g)
For the cotton results I took the 5th result out, because it is the odd one out. To make the test fair, we worked out the mean for each thread by adding all the results and dividing it by the number of which we tested each thread and that was seven, but not cotton because as I mentioned earlier I took one of the results out, so I divided it by 6 instead of 7.
From the results above we can really see the strength difference between synthetic and natural fibres. The results are clearly showing us that natural fibres are stronger than synthetic fibres.
Most of the results for the threads are reliable. There is only one outlier, and the others had small differences.
The data was collected safely and only minimal safety procedures, such as using a lab coat to cushion the fall of the weights, were needed. However, it was difficult to tie all of the knots in the same way and to ensure they were secure. An easier way of attaching the threads to the clamp stands would have helped to make the results more accurate. The clamp stands were also not the correct height, as the fibres stretched, making the height needed larger. Taller clamp stands could have been used to ensure this did not happen.
My conclusion is quite reliable as most of my data is reliable. There is also a smaller probability of unnoticed anomalies being included because each fibre was tested seven times. The techniques used were easy to repeat if care and time was taken. I think that because of these factors I can have a high level of confidence in my conclusion being correct.
The differences in the strengths of the fibres could be caused by human error. It is possible that the fibres were pulled and weakened or that more knots were tied in the fibres than in other tests for the same thread.
There was not enough time to thoroughly investigate the strength of the thread. We were sometimes rushed and could have made mistakes because of our haste. We could also have tested the fibres more and tested a larger number of fibres if we had had more time to conduct the experiment.
We did not check that the weights were all the exact weight that they were marked as being. This means that some of the weights could have been lighter or heavier than perceived and outliers may be due to this.
The outlier could also be because of an actual difference in the strength of the fibre. The results for the first cotton, for example, are very varied but none of them are extremely far from the other results. This could be because the fibre’s strength varied or portions of the fibre could have been weaker.