Count a complete trip
One oscillation returns to the same side after passing the middle twice.
Pendulum Clock
Change string length and bob mass while timing complete small angle oscillations.
Grades 3–5 · Physics
Your goal
Tune the pendulum to a 2.01 second period, then count 1 whole oscillations. Try changing bob mass to check whether the period changes.
Reduced motion is on. The controls still update the scene.
One complete oscillation takes 2.46 s. 0 complete oscillations take 0.00 s. A 1 kg bob has the same ideal period as any other mass at this length.
m
kg
Each click records a whole oscillation and updates the stopwatch without autoplay. This small angle model uses T = 2π√(L/g) with g = 9.8 m/s². String mass, air resistance and friction are ignored. Length is measured from pivot to bob center.
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Learn with Pendulum Clock
Pendulum Clock lets elementary students tune a pendulum and count complete oscillations with a virtual stopwatch. Change the distance from the pivot to the bob center, choose a bob mass, and record one full trip at a time. The drawing marks both swing extremes so learners can distinguish a complete oscillation from a single crossing. Timing goals encourage comparisons between lengths and repeated trials with different masses. Children find that a longer pendulum swings more slowly while bob mass does not change the period in this ideal small angle model.
What to look for
Change only length
A longer pendulum takes more time for each complete oscillation.
Compare bob masses
Keep length fixed and change mass to test whether the ideal period changes.
For teachers and curious learners
Discover that small angle pendulum timing depends on length rather than bob mass. Ask students to predict what will happen, change one setting, and explain what they observe. Learn gives a starting point. Practice and Challenge offer new goals with the same scene.
The small angle pendulum relation uses gravitational acceleration 9.8 m/s² and an 8 degree release angle. String mass, friction and air resistance are ignored.