ACTIVITY 2 - HOW TALL IS… ?

Tuesday November 30th, 2010Rollie Comeau

Watson Lake Secondary School

ACTIVITY 2 How tall is …?

Specific OutcomesA.3 - 3.1 and 3.2B.2 - 2.3 and 2.7B.3 - 3.5, 3.6 and 3.7B.4 - 4.1 and 4.2B.5 - 5.1, 5.4, 5.7, and 5.8

ACTIVITY 2 How tall is …?

Material needed:Protractor Tube (one foot long)Tape StringWeight PencilPaper CalculatorWarm Clothing

ACTIVITY 2 How tall is …?

ProblemYou need to cross a particularly swiftcreek. It is too wide to jump. A tree

stands close to the edge of the creek.How can you determine if the tree is

long enough to safely span the creek?

ACTIVITY 2 How tall is …?

Tree

Ground Distance

ACTIVITY 2 How tall is …?

To solve this problem, the concepts ofsimilar triangles, right-triangles,trigonometry, parallel lines and

transversal lines, and/or referents canbe introduced in your lesson.

ACTIVITY 2 How tall is …?

Let’s use trigonometry to solve this problem.

The three basic trigonometric ratios involve two sides of a right-triangle and one of the two acute angles.

ACTIVITY 2 How tall is …?

In our case, we are looking for the height of the tree - this is the

unknown value we are seeking.

ACTIVITY 2 How tall is …?

The distance from the tree can be assessed with the help of a long

measuring tape.

This is one of our known values.

We are missing an acute angle…

ACTIVITY 2 How tall is …?

From the ground, looking up at the top of the tree, we could possibly determine the angle of elevation. For this, you will need to consult a surveyor who can measure it for you or, construct a simple device

that can do it for you!

ACTIVITY 2 How tall is …?

A simple clinometer comes to mind…

let’s construct one!

ACTIVITY 2 How tall is …?

Before going outdoors, you will need to determine the height of your eyesight.

For convenience, a measuring tape has been placed on the wall to assist you. Record this value on the Activity 2 data sheet provided.

ACTIVITY 2 How tall is …?

As a group, select a set distance from the object to be measured. Record this value as “Ground Distance”.

ACTIVITY 2 How tall is …?

Each member of the team should:a) Use the clinometer (viewing through

the tube at the top of the tree)b) Take the reading off the clinometer

(angle in degrees)c) Record the measurement read by b)

ACTIVITY 2 How tall is …?

Upon return, a) Draw a diagram representing the

problem we are attempting to solveb) Place all measurements in the

diagramc) Use trigonometry to solve the

problem

ACTIVITY 2 How tall is …?

Share your answer with your group.1. Discuss why your answer may

vary compared to others.2. Discuss factors that may

influence your answers.