This lesson should be completed on a sunny day.
Give pairs or groups of students two meter sticks or yardsticks,
string, and scissors. Have the students measure each other's height
with the string and use the meter stick to measure the string. Students
should record their individual data on the In Your Shadow activity sheet.
Within groups, students should be consistent when measuring, using either all metric measurements or all customary measurements.
Have students measure each other's shadow, following the same
procedure as that for measuring height. Once again, record the data on
the activity sheet.
Next, ask students to measure the shadow of something tall,
such as a flagpole, a school building, or a tree. Once the data is
collected on one or more objects, return to the classroom and post the
data on the chalkboard or overhead. (You may assign different groups of
students to measure different objects while outside.)
Ask the students how they might find the height of the tall
object just by knowing the length of its shadow. Discuss what the word
"similar" means in reference to geometry.
Next, help the students see how to use proportions to
determine the heights of the tall objects that they measured. For
example, show students how to use the measurement of the shadow of a
tree along with a student's height and shadow measurements to figure
out the height of the tree. The three pieces of known data can be used
to set up a proportion with one unknown.
Work with the students on setting up proportions to solve for
missing measures. Offer several examples using the data that the
students collected in the experiment.