CAN PENDULUMS COMMUNICATE?

Materials Iron stand String

clamp w ei ght s

AMY ROSE S. LAYCO

In this activity, you will learn the basic principles of vibrations and waves. The knowledge with what you will learn can explain many interesting applications particularly in communication.

Obj ect i ve

Integrate basic principles of vibrations and waves in explaining how pendulum can communicate.

Pr ocedur es

1. Set up the apparatus shown in the figure below with the support stands about 50cm apart and clamped securely to the lab bench.

2. Connect the stands with a string, and make sure the string is taut. 3. Suspend two pendulums (about 30 cm) of equal mass (50 g) from the string. Ensure the masses are securely attached to the string.

4. Predict what will happen when you start one pendulum swinging. 5. Gently start the pendulum swinging. Watch carefully for several minutes. Record your observations.

6. Shorten the string on one of the pendulums to about 20 cm, repeat the above step.

Appl i cat i ons

1. In what way can it be said that the two pendulums “communicate” with each other?

2. One of the observed motions is called a “forced vibration” and the other is called a “sympathetic vibration”. Which motion is which? Explain your answer.

Concl usi on

Hirsch A. 2008. Physics 12 College Preparation. Singapore. Thomson Learning Asia.

Exemplar Lesson Plan in Science

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The author is SST II at LUBAO National High School