Teach lesson
Which pendulum swings faster?
Count and time two real pendulums to find out whether the shorter one completes its swings sooner.
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Learning Outcomes
Recognize one complete swing as a journey out and back.
Compare the time for the same number of swings in two pendulum configurations.
Use the measured times to decide which pendulum completes its swings faster.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
1 · Out and back
4 min
A playground swing travels out and back. A pendulum does too: a weight hangs from a support and swings from side to side. Could a shorter pendulum complete its swings sooner?
We will choose two real pendulums in the lab and watch their recorded motion. Faster here means taking less time to complete the same number of swings.
The lab calls this pendulum Standard. We will compare it with Short.
Tell a partner your prediction: Standard, Short, or about the same. You can change your mind after the experiment.
Practise counting: start on the left and say “zero”. Go right and come back left: say “one”. Right and back left again: “two”. Each whole out-and-back journey counts once.
Left → right → left is one complete swing. Practise the movement with your hand.
2 · Time 20 complete swings
14 min
In your pair, one person counts aloud while the other operates the lab stopwatch. Practise together with your teacher before starting. Read the steps before playing your video.
Open the Pendulum lab. Select Start configuring → Standard → Choose parameters. Set the angle to 15°: this is how far the pendulum is pulled aside before release.
Select Start observing. Press the stopwatch's RESET while the pendulum is being prepared.
As soon as the released weight first reaches the left end, say “zero” and press TIME to start the stopwatch.
Count 1, 2, 3…20, once each time the weight comes back to the left end. At 20, press STOP. Do not count the right end. Write down the time in seconds.
Select Back to parameters → Back to pendulum selection → Short → Choose parameters. Keep the angle at 15°.
Select Start observing, reset the stopwatch, and time 20 complete swings in exactly the same way. Write down the Short time.
After using both pendulums, return to this activity, select Mark practice as done, and enter your two times below.
Standard time
How many seconds did Standard take for 20 complete swings? Enter the time you measured.
Short time
How many seconds did Short take for 20 complete swings? Enter the time you measured.
3 · What do your times show?
5 min
Compare your two numbers. The shorter time means the pendulum completed the same 20 swings faster.
Your conclusion
Which conclusion fits your measured times?
Point to the two times and tell a partner: “I chose this because…” Did the evidence change your prediction? Then submit your answers.
Extra challenge — optional: for a steady tick-tock beat, which of these two pendulums would you choose for more complete swings in one minute? Explain aloud using your comparison. You do not need another experiment.
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