# Watch it Swing and Count the Periods!

Pendulums:  To and Fro We Go

Today’s lesson focused on pendulums.   The motion of pendulums was one of the many phenomena investigated by the famed scientist Galileo over 400 years ago and what he learned about them had a huge impact on the history of technology. The periodic motion of pendulums allowed for the invention of clocks and the standardization of time, and they still have many uses in modern society.

Students saw that a pendulum consists of a pivot point with a rope or wire attached to it and a mass on the end. The time it takes the pendulum to make one full oscillation back and forth is called the period. Here, gravity is the only force working on the pendulum. If we took the same pendulum and put it on the Moon, the pendulum would have a slower period due to less gravitational force. Some examples of items that use pendulums are metronomes and grandfather clocks.

For the activity, students constructed their own pendulums and then changed the variables of it to see if mass, length, or angle affected the period of a pendulum. They were surprised to learn that only length caused the period to change:  a longer length correlated to a longer period. Students also learned that gravity works on different masses in the same way, so mass is not a factor in the period of the pendulum.

Students really enjoyed this activity!

To experiment with virtual pendulums at home, check out: