Engineers Solve Problems

Activity 5:
How Tall Is That Flagpole Anyway?

TIME REQUIRED

Two or three 50-minute lesson periods.

LESSON RATIONALE

Engineers are also involved in solving problems related to stationary structures.   These structures require foundations that are below the surface of the ground.   The strength of the soil (ground) is used to counterbalance other forces acting upon the structure above ground.  These external forces are wind, snow, and possibly earthquake.

CONCEPTS, UNDERSTANDINGS, SKILLS

Engineering:

1. Forces are caused by external elements such as wind, rain, snow, and earthquakes. Force is exerted on a body by the element; for example, snow causes a force to act upon a roof.
2. A moment is a force times a lever arm or distance.  Here the lever arm is the distance from the pivot point to the location of the force.  The pivot point can also be called the fulcrum.

Mathematical:

1. Use of mathematics to illustrate equilibrium, which keeps a body stationery.
2. Simple equation solving.
3. Substituting values in an equation to solve for an unknown.

In addition to equations, students will need to understand variables, unknowns, and subscripts.

MATERIALS NEEDED

1. Sticks of various lengths to simulate flagpoles.
2. Quantity of clay, sand, or other materials into which to put the simulated flagpoles.
3. Classroom set of copies of student reading.

LESSON OBJECTIVES

Students will:

1. Know how a structure and its foundation must react to external forces.
2. Understand that wind exerts a force against objects.
3. Know how forces and reactions can balance each other to keep an object in place.

SUGGESTED PROCEDURES

1. Demonstrate the concept of balance using the clay, sand, or other materials and the "flagpoles," including the actual classroom flagpole, if one is available.   Have class decide whether the size of the flagpole determines the amount of clay necessary to hold up the flagpole and speculate on the reasons why this is so.
2. Distributed the reading, and work out the demonstration problem with the class.

ENRICHMENT ACTIVITIES

1. Have students discuss what other forces may affect the forces on the flagpole (such as extraordinary weather conditions, weight of the pole and flag, and soil conditions).
2. Have some students find the specifications for the school flagpole and determine the size of the base.  Have them compare their results with the actual measurements of the base.
3. Suggest experiments and readings on levers and balances.