Metrics

In the United States our measurements are usually based on the imperial system from Great Britain. This British system of measurements which includes units such as feet, pounds and gallons has deep historical roots. For example, the foot is thought to be the length of the foot of King Henry I of England in the 12th century whereas the pound is based on the Roman word libra (lb) which is the equivalent to the weight of 7,000 grains. Scientists, however, decided to adopt a different measurement system because of its tremendous advantages.  The metric system (see table 1), the most commonly used standardized system worldwide, not only covers a large scale and its measurements are also in consistent units of 10 (see table 2) which makes calculations simpler.

Since many people in the United States are used to the imperial system, we must become familiar with the metric system. Often we need to convert between the two systems. Below are some helpful conversions.

Conversions Between Imperial and Metric Systems

1 kg = 2.2 pounds

1 km = 0.62 miles

1 m = 39.37 inches

1 inch = 2.54 cm

1 l = 1.06 quarts

The following activity will help you review the scientific method as well as work with the metric system. To learn more about the history of how the metric system was implemented, you can watch this video:

Title: __________________________________________________________________________

(Note: At the end of the experiment, you will create a title.)

Background 

Observation and question: People have observed that a person with a longer upper or lower limb tends to be taller. We then asked the question: “Is the length of a person’s upper limb directly proportional to his/her height?” Two measurements (variables) are directly proportional if, for example, as one amount increases, the other amount increases at the same rate. The upper limb spans from the armpit to the end of the fingertip.

Hypothesis and prediction: If the length of a person’s upper limb is directly proportional  to height, then the ratio of upper limb length to height for all subjects must be constant, i.e., the same.

Purpose

· Use the metric system

· Review steps of the scientific method

Materials

Measuring tape/tool  or meter stick or measuring app on phone: Ruler for Android (Links to an external site.) , Measure App on Apple or piece of paper (8.5 x 11) to use as a measuring device

3-4 human subjects

1 calculator

Procedure

1. Pick 3-4 subjects from group members.

2. Each subject puts right arm straight out (parallel to the ground).

3. Using the meter stick or measuring tape/tool, measure upper limb length (from arm pit to the end of the finger tip) of subject 1 in cm.

4. Record measurement in Table 1 below.

5. If subject 1 does not know height, then measure height in inches and cm.

6. Practice converting height in inches to cm. Show work below.

7. Record height of subject 1 in cm in Table 1 below.

8. Calculate ratio of upper limb to height of subject 1 and record in Table 1.

9. Repeat measurements and calculations for all subjects and record in Table 1.

Results:

Table 1. Comparison of Limb Length to Height in Group Subjects

* 1 inch = 2.54 centimeters

Subject 1, 2, 3 and 4 had a ratio of upper limb length to height of

_____, _____ , _____ and ____ respectively.

Average of group subjects’ ratio of upper limb length to height was  __________.

Average of all class subjects’ ratio of upper limb length to height was   _________.

Discussion/Conclusion (~1 sentence each):

1. Do your results support or reject the original hypothesis? Explain your answer.

2. Based on an analysis of your data and the class data, what conclusions can you make?

3. Describe one future experiment you would like to do to extend or make these findings more reliable.

Metric System Practice Problems (Optional) 

Note: For metric system, know how to convert within the metric system (ie. meters to mm, mg to grams). Also, know how to convert between the metric and imperial system.

1. A pen is approximately 12 (µm mm cm   m).  Circle one.

2. A chair is approximately 2 (nm cm m km) high. Circle one.

3. Convert the value on the left into the unit indicated on the right of the equation below.  Show work.

a. 2,346 m = ____ km

b. 5 ft, 9 in = _____ cm (1 inch = 2.54 cm)

c. 6 km = _____ miles (1 km = 0.62 miles)

d. 208 mL = ____ L

e. 2.67 kg = _____ g

f. 80 nm = ______ m

4. Joe weighs 152 pounds. What is his weight in kg? Show work. (1 kg = 2.2 pounds)

5. Mary’s height is 175 cm. Mark’s height is 5 ft 6 in. Who is taller?

Explain and show work. (1 inch = 2.54 cm)

(Hint: convert Mary’s height into inches, OR convert Mark’s height into cm)