Swings as Pendulums
Discovery Based Physical Science Activity Lesson Plan
Use children on swings as pendulums to investigate the properties of pendulums. This discovery based activity is adaptable to any grade level.
For the Teacher
Pendulums, an example of simple harmonic motion, are good for discovery based physical science laboratory activities. By varying the depth of the analysis expected, the activity is adaptable to any grade level. The experimental apparatus is simple and inexpensive enough for even impoverished school districts. The experimental design is also simple enough that students can learn by designing their own experiments.
Equipment Needed
You can make a pendulum by suspending any weight on a piece of string and allowing it to swing back and forth. However, the activity will be more fun and memorable for the students, without compromising the academic quality, if they go out to the playground and swing on the swings. It is important that the children do not pump the swings in any way while the swings are being timed. To investigate the relationship between the time to make one complete oscillation, called the period, and the length of the pendulum, you will need swings of different lengths.
You will also need a stopwatch to measure the period of the pendulum. If your science department doesn't have any, try the physical education department. Most digital watches also have a stopwatch function. As a last resort, have students count off seconds or use their pulses, like Galileo, as timing devices. Tip: If the students have learned division, the period can be measured more accurately by timing more than one oscillation and dividing the total time by the number of oscillations.
You will need a ruler or tape measure to measure the lengths of the pendulums.
The Activity
The time for one complete swing or oscillation is called the period. The angle the pendulum swings through is called the amplitude. The distance between the pivot point of the string (or top of the swing) and the oscillating mass is the length.
For the activity have the students investigate the relationships among these variables to answer the following questions.
- Does changing the amplitude of the swing change the period? (It does not.)
- Does changing the length of the pendulum change the period? (It does.)
- Does changing the amount of mass on the end of the pendulum change the period? (It does not.)
Allow the children to work in small groups and design the experiments needed to answer the questions. That is what real scientists do. They do not start with a prescribed experimental procedure; they start with a question.
For the first question, don't let the amplitude get too large.
Many children and adults are sensitive about their weight, so the third question requires some sensitivity. Rather than risk labeling a child as fat or skinny, it might be better to use an average sized child and an adult as the small and large masses.
All three questions can be investigated in a single long period, or the activity can be spread over three days with one question each day.
Analysis
Adapt the level of analysis to the student's grade level. For young elementary students, the period gets longer, shorter, or remains the same is sufficient. For high school or college physics classes, require a detailed mathematical and graphical analysis. Simply adjust the level of analysis to the mathematical skills of your students.
To give students a taste of what real scientists do, have them present their results to the class in a mock scientific conference.
Further Reading
Hecht, Eugene, Physics: Algebra/Trig 2nd ed., Brooks/Cole, 1998, Chapter 10.
Any physics textbook should have a chapter on simple harmonic motion.
More Science Activities
Planetary Interiors Lesson Plan
Jupiter, Venus, Comets, & Velikovsky
