Skip to main content

Physics of Media Arts: Conceptual Physics for Students of the Media Arts

Aaron Wong

Lab Activity 2.8.2 The Metric System is the Tool of the Devil!

Introduction.

“The metric system is the tool of the devil! My car gets forty rods to the hogshead, and that’s the way I likes it!”
―Abraham Simpson (Grandpa Simpson)
While most of the world and all of science operates using the metric system, daily life in the US usually revolves around the imperial system of measurement. This is the system of quarts, gallons, feet, and miles that you’re probably most accustomed to seeing. In fact, there are only three countries in the world that officially operate on the imperial system! (The other two countries are Liberia and Myanmar.)
The reason the imperial system is called that is because it was originally the system of units imposed on countries by the British Empire during the time of colonialism (imperial means "of the empire"). Somewhat confusingly, the imperial system wasn’t formalized until the 1820s. Before that, there was a vast array of customary measures used in various locations, some of which date back to the 1500s (and potentially even earlier).
The actual origins of individual measurements were often rather arbitrary. For example, the length we call a foot today was originally the length of King Henry I’s foot. And an inch has been defined muliple ways, including the length of three grains of barley laid end-to-end and the length of twelve poppy seeds. There are also other historical measurements that are similarly arbitrary, such as a cubit (the length from your elbow to the tip of your outstretched middle finger) and a league (the distance a person can walk in an hour). Of course, differences in individual human bodies made these measurements to be rough estimates at best. And the convoluted history and origins of these measurements have led to the equally convoluted relationships between them, such as 5280 feet in a mile.
For this lab, we are going to explore some more of the history of different units and practice making unit conversions using the imperial system.

Procedure.

This lab consists of a lot of calculations. When doing your calculations, show the multiplication by the appropriate conversion factors and make sure that the units cancel appropriately.
  1. As noted above, an inch has been interpreted as being the length of three grains of barley laid end-to-end and as the length of twelve poppy seeds. From this information, estimate the average length of a grain of barley and the average length of a poppy seed. (Use a three digit decimal approximation.)
  2. Research the size of grains of barley and poppy seeds. How close are your calculations in the previous step to the values you found?
  3. Sticking with the historical relationships, we can establish two length equalities: \(1 \text{ inch} = 3 \text{ grains of barley}\) and \(1 \text{ inch} = 12 \text{ poppy seeds}\text{.}\) Use these relationships to perform the following unit conversions:
    • Convert 5 feet to poppy seeds.
    • Convert 12 yards to grains of barley.
    • Convert 2 miles to poppy seeds.
    • Convert 600 poppy seeds to grains of barley.
  4. Another set of linear units were used for agricultural purposes. These are rods, chains, and furlongs. A chain is 4 rods, and a furlong is 10 chains. If you are familiar with horse racing, you probably know that there are 8 furlongs in a mile. From this information, determine the length of rods, chains, and furlongs in feet. Then perform the following unit conversions:
    • Convert 200 yards to chains.
    • Convert 100 feet to rods.
    • Convert 1 furlong to poppy seeds.
  5. Liquid measurements often developed from commercial operations involving alcohol. You might know that both wine and whiskey are aged in barrels, but you might not know that the traditional sizes of the barrels are different for each beverage. Barrels are also related to other cask sizes, such as a hogshead and a tun. We are going to focus on the wine cask units, where a tun is 210 gallons, there are 4 hogsheads per tun, and 2 barrels per hogshead. Convert the quantities of barrels and hogsheads to gallons.
  6. If Grandpa Simpson’s car gets forty rods to the hogshead, how many miles per gallon is he getting? Is this good or bad? How many barley seeds per tun does he get?

Discussion.

These questions will ask you to reflect on your experiences doing these calculations.
  1. You calculated the number of poppy seeds in 2 miles. If you were to line up that many poppy seeds, do you expect the actual total length to be close to 2 miles? Why or why not?
  2. It is likely that there was never a direct connection between the lengths of grains of barley and furlongs. Why do you think this is the case?
  3. Do you think that the units of rods, chains, and furlongs is more or less "logical" than feet, inches, and miles? What features do you think make for a "logical" system of measurements?

Conclusion.

This lab activity is mostly about practicing your unit conversions. Hopefully, you are more comfortable with them after having completed it.

Lab Write-Up Guidance.

Use the following outline to help you write up your lab report completely and correctly.
  • Title and Header.
    What is the title of the lab and who was in the lab group?
  • Introduction.
    In your own words, what was the purpose of the lab activity? This should only take a few sentences for this lab.
  • Procedure.
    Since this lab is mostly doing calculations, the procedure section should explain the general process of performing unit conversions.
  • Results and Data.
    Provide a careful writeup of the calculations you did.
  • Discussion.
    Answer the discussion questions. Be sure that you state the original question and organize it in a way that is easy to follow.
  • Conclusion.
    Write a few sentences explaining your experience with the lab. Do you feel better with unit conversions than you did before?
PrevTopNext