The document summarizes an experiment measuring the breaking strength of human hair. Students worked in groups to collect force and hair breakage data from volunteers. Each volunteer's hair provided 10 individual strength measurements that were averaged. The class averages and uncertainties for each student were also calculated. The data showed variation in average hair strength between individuals but no clear correlation to factors like gender. Improvements suggested were comparing results by ethnicity, hair color, or location on the head.

1. Lauren Ruzinsky
September 22, 2011
Human Anatomy P. 7
Hair Strength
Human hair grows from follicles found in the dermis. It is made up of a protein called
keratin. This is strong and flexible, which allows hair to have shape and movement. In
this activity, we are going to measure a person’s hair strength, or rather how much force
it takes to break a human hair.
The only pieces of equipment that were needed were a force probe, a computer with
Logger Pro software, a pencil, a sheet of paper, and many strands of hair. First, the class
split into groups of three to four people and set up their own equipment. The force probes
had to be calibrated with Logger Pro. The next step was to measure the breaking strength
of the hair. We did this by looping a strand of hair over the force probe and gently pull
straight down until the hair breaks. We recorded 10 readings of the highest forces in
newtons for each person in our group (shown in Figure A). Our final step was recording
the class averages and uncertainties of hair strength (shown in Figure B).
Strand 1 2 3 4 5 6 7 8 9 10
of hair
Force 1.55 2.13 1.46 1.23 0.86 1.98 1.69 0.68 1.79 1.49
(n)
Figure A- Personal Profile of hair strands
Formula for average: Amount of forces added together divided by number of strands of
hair. Therefore, personal average is 1.486 newtons.
Formula for uncertainty: High minus low divided by two. Therefore, personal uncertainty
equals 0.725.

2. Student Name Average Hair Uncertainty Gender
Strength
James 3.08 0.26 M
Chloe 3.33 0.76 F
Brooke Solorio 1.19 0.37 F
Carly Bessette 1.62 0.395 F
Sarah Cano 1.45 0.635 F
Brooke Schaffner 2.654 0.96 F
Jennifer Purgill 2.802 0.23 F
Brianna Phelps 1.624 0.575 F
Jessie 1.15 0.452 F
Srei 1.91 0.975 F
Mel 1.72 0.841 M
Lauren 1.486 0.725 F
Paul 2.44 0.195 M
SoYeon 2.064 0.475 F
Niv 0.98 0.91 M
Jenn 2.109 0.82 F
Michaela 1.016 0.255 F
Figure B- Class Profile of hair strands
The data has a range of numbers that do not show an immediate correlation between the
average hair strength and any other factors such as gender. Some improvements could
have been made to this lab activity. One would be to compare a person’s ethnicity or hair
color to the hair strength. Another would be to pick hairs from different regions on the
head. This can give more varied results.