Experimental Physics Report - Unexpected Results

[Tantalum]

Hi everyone I have a quick question in regards to an experimental report I'm writing for my year 11 Physics class. Basically we have to test different variables that could effect a bungee cord fiber in relation to stress and strain by increasing the weight force on the fiber until it snaps. For the first part of the experiment I tested the effects of increasing the number of fibers.

The problem I face is that when I measured the diameters of the different grouped fibers using a digital caliper the single fiber was 0.13mm, three fibers was 0.26mm and five fibers was 0.25mm. I just want to know if anyone know why this might be the case, as it also happened when I was making different composite fibers. The method I used for making groups of fibers more than one was by clamping one end and spinning them.

Personally I think the fibers may be pressing into each other and causing the diameter to be smaller than expected. I just need someone to confirm this and explain further; or shows me what's really happening.

Thanks in advance,
Max

 

[SteamKing]

What happens if you take several fibers with identical diameters of 0.13 mm and arrange them in different bundles.
For example, three smaller fibers are not going to lay side-by-side, they are going to pack into something which resembles a triangular cross section, like this:

O
OO

If you really want to find out how the strands with different numbers of individual fibers pack, soak a short length of the middle of your rope in some strong glue, like epoxy. When the glue has cured, cut the rope in two and examine the ends with a magnifying glass.

 

[SteamKing]

Page 1 of this attachment shows the cross section of different rope braids:

http://www.bairstow.com/media/pdf/safety/N7806.pdf

 

[Tantalum]

Thank you, this helped allot.

 

[Nickie]

Hello Max,

Thank you for sharing your experimental results and question with us. It is always important to carefully analyze and interpret unexpected results in science, as they can often lead to new discoveries and insights.

Based on the information you provided, it does seem likely that the fibers are pressing into each other and causing the smaller diameter measurements. This could be due to the spinning method you used, which may have caused the fibers to compact together. Another factor that could contribute to this is the elasticity of the fibers themselves, which may cause them to compress when clamped and spun.

To confirm this hypothesis, I suggest conducting further experiments where you vary the spinning speed and the clamping force to see if it has an effect on the resulting diameter measurements. Additionally, you could also try using different types of bungee cord fibers to see if they exhibit similar behavior.

Overall, it is important to carefully control and consider all variables in your experiment to ensure accurate and reliable results. Keep exploring and questioning your findings, as this is the essence of scientific inquiry. Good luck with your report!