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Home > Education > Activities and Resources for Earth Science Teachers > Activity #40


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  Teacher Sheet  

Activity #40: The Scoop on Slope (y=mx+b)

OBJECTIVES

Students will construct a slope measuring device, measure a series of slopes, and relate the concept to physical structures around them.

TIME

One 45 minute period, students working in groups of three.

BACKGROUND

What do a mud slide, an avalanche, or an extreme erosion event all have in common? All are common tragedies in the newspaper or on television. They also have one physical character in common, and that is the concept of slope. Slope may be defined as a measurement of the steepness of a surface. Students may also have definitions of "rise over run" and "vertical drop over horizontal distance" depending on their math experiences. The measurement of slope is a common practice with engineers, surveyors, foresters, housing contractors, architects, and numerous other professionals. It is also found in laws and established standards for road construction, building access ramps, mining, and many environmental factors.

In this exercise students will construct a simple slope measuring device (clinometer) and measure a series of slopes within their own school's area. Professionals may measure slope in a number of different units. Two units are used in this activity and will be compared later in the exercise.

MATERIALS

Each group of three students will need the following - a soda straw, a piece of stiff cardboard, some string, paper and white glue, masking tape, a small weight (quarter-ounce lead barrel sinkers work well), copies of clinometers (see attached sheet), and scissors. Each student will also need pens and their notebook.

PROCEDURES

Have students glue model A or B from Figure 2 to the piece of cardboard and cut out around the outside margin. Using the tape, attach approximately 12 inches of string to point X on the clinometer you have selected to work with. Attach the small weight to the end of the string; the string must swing freely from point X. Using two or three pieces of tape, attach a soda straw along the straight edge of the scale. This will be your sight. See Figure 1 for steps 2, 3, and 4.

Have students select three slopes around the school grounds. One of the group will act as a target; this person stands at the top of the slope. Another student sights through the clinometer at the nose of the target student (see Figure 1). The third partner reads and records the position of the string as it crosses the scale. Students should swap jobs so all have a turn using the clinometer. See data table on student pages.

SPECIAL SAFETY PRECAUTIONS

None.

FOLLOW-UP

Have the students describe some of the variables that will affect the accuracy of their measurements (e.g., a four-foot student viewer using a six-foot student target).

Determine and discuss how slope is applied to:

  1. The crown of a road
  2. Switchbacks on steep mountain roads
  3. A flight of stairs
  4. Mudslides in California
  5. Rain runoff on your lawn
  6. The entry ramp at the grocery store
  7. Erosion in a plowed farm field
  8. Building a railroad

Have students locate a copy of your town or city building codes for house lots or roads and determine if there is any reference to slope in the standards. If there are references, have students discuss why they are there.

Slope may be measured in degrees, but engineers use percent slope for their unit of measurement. If students used different units to measure slopes, have them compare these measurements and try to mathematically relate % slope to slope in degrees.

SOURCE

Activity developed by James H. Barden, in conjunction with the 1991 CREST intern program.

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  Student Sheet  

Activity #40: The Scoop on Slope (y=mx+b)

PURPOSE

To construct a device to measure slope and use this device to find out the slope of structures in your immediate school environment.

MATERIALS

For this activity you will work in groups of three. Each group will need the following: a soda straw, a piece of stiff cardboard, a piece of string about 1 foot long, paper, white glue, masking tape, a small weight, a paper copy of the clinometers (Figure 2), a diagram of the finished product (Figure 3), and scissors. Each student will need their pens and notebook.

PROCEDURE

A device which measures a slope is called a clinometer. The following steps apply to the construction of the clinometers you will use in this exercise.

1. Glue EITHER model A or B from Figure 2 onto a piece of stiff cardboard and cut out around the outside margin.

2. Using tape, attach approximately 12 inches of string to point X on the clinometer model you have chosen to work with.

3. Attach the small weight to the end of the string; the weight and string must swing freely from point X.

4. Using two or three pieces of tape, attach the soda straw carefully along the straight edge of your scale. This will be your sight. See Figure 3 for steps 2, 3, and 4.

The next steps apply to using your clinometer to take slope readings.

5. With your partners, select three sloped areas around the school ground to measure.

6. With one of the partners as a target at the top of the slope, a second partner sights through the straw at the NOSE of the target partner (see Figure 1). The sighting partner needs to hold the clinometer very steady.

7. The third partner reads and records the position of the string as it crosses the scale.

8. Partners switch positions and allow all members of the group to measure the same object.

9. Complete the attached data table; fill in the name/location of each slope.


DATA TABLE
OBSERVERSLOPE #1SLOPE #2SLOPE #3
1


2


3


Average Slope


Answer any of the following or perform any of these activities as directed by your teacher.

QUESTIONS

1. List and explain some of the factors that will affect the accuracy of your clinometer. Be specific.

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2. What pieces of equipment could you add to your clinometer and its use that would increase the accuracy of this device. (Hint - look up the term stadia rod).

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3. Determine the mathematical relationship between percent slope and degrees of slope?

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Last updated on October 6, 2005