ASL
We want to find the maximum length a hair can grow. The units for rate of growth are mm/day. The unit for length is mm. The variables that we will use in the model are:
- length of anogen (growing phase) in months or years
- length of telogen (resting phase) in months or days
- rate of growth in mm/day
ASL
If the time unit is in months then multiply the number of months by 30.5. For example 4 months = 4 months X 30.5 days/month. The month units cancel out 4months * 30.5 days/month . 4 * 30.5 days = 122 days.
The answer is 122 days.
ASL
There are 365 days in a year. If the time unit is in years then multiply the number of years by 365. Example: 6 years = 6 years * 365 days/year. The year units cancel out 6 years * 365 days/year. The answer is 2190 days.
ASL
There are really 365.25 days in a year if you consider leap year. Is it important to include the .25 in our calculation?
ASL
We want to find the maximum length a hair can grow. The units for rate of growth are mm/day. The unit for length is mm. We need a math operation that will change mm/day to mm. If we multiply days by mm/day the days cancel out days * mm / day. Therefore we are left with mm. .
ASL
Using the same steps for finding the maximum length. we can find the terminal length of the hair by multiplying the growth time by growth rate. For example 122 days * .15 mm/day. This = 18.3 mm*day/day. The day units cancel out.
The longest the hair will grow is 18.3 mm.
ASL
How do we determine the time that the hair grew? Is it the length of: anogen, telogen, or anogen + telogen?
Because the hair only grows longer during anogen phase we use the length of anogen.
ASL
We have 3 models to help you calculate the terminal length of the hair. The models were written in Excel, Stella, and JavaScript. Ask your teacher which model to use. Use the Rates and time data from the science page.
ASL
How many years would your scalp hair need to grow to be 60 cm long?
ASL
How many years would your scalp hair need to grow to be 90 cm long?
ASL
How many days would it take to grow a beard of 15 cm?
ASL
Measure one of your eyebrow hairs. How many days would the hair need to grow to reach this length?
ASL
Compare the results for all of the students in class. What is the range?
ASL
Measure one of the hairs on your arm. How many days would this hair need to grow to be this length?
