The Stand Of The Pencils

SCIENCE CONCEPT:

The center of gravity is the point in an object where the entire mass of the object seems to be concentrated. A force acting upward at this point equal to the weight of the object would support the object. The object would be stable. It would balance.

STUDENT OBJECTIVE:

The student will experiment with two pencils and observe each of their centers of gravity.

OVERVIEW:

In this activity, the student will stand two pencils upright and then release both of them at the same time. The student will observe what happens to each pencil and why they react the way they do.

PREPARATION TIME:

No time.

LESSON TIME:

15 minutes.

TEACHER PREP:

Gather the materials that are needed for the experiment.

WORDS TO KNOW:

COG (center of gravity)

arc

mass center

horizontal

TEACHER TEXT:

The theory of gravity for which Sir Isaac Newton is famous for proves valuable in many aspects of our modern life. Airplanes have to be so constructed and powered that they can successfully resist the force of gravity. To ensure stability, airplanes are designed with the COG (center of gravity) in mind. Keeping the weight forward and low keeps aircraft from toppling sideways, pitching, and nose-diving. Cars and trucks, especially tall vehicles, have to be made with their centers of gravity low enough to withstand any tendency to topple over when driven around sharp corners. Engineers have to work out complicated mathematical formulas to find the center of gravity of the object that they are working on. We can use two pencils, one short and one tall, to find out about the center of gravity.

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Last modified: Tue Mar 17 15:41:20 PST 1998