TalentJR apps
You need: a string, a small heavy nut or washer as the bob, a pencil taped to a table edge, a ruler and a stopwatch. What happens: the bob swings back and forth at a steady rhythm. A longer string swings more slowly; a heavier bob takes almost the same time. Why: gravity pulls the bob down and it swings through to the other side; the time for each swing depends on the length. Timing 10 swings and dividing is more accurate than timing one.
✓ You passed this lesson’s test.
Only the length matters — “swing time depends on the string length, hardly on the weight of the bob”
Use it for: Class 7–9 lessons on motion and time; the classic fair-test science project for kids.
Check: A string 4 times as long doubles the swing time ✓
▶ Watch it animatedWork it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.
Right: 0 · Tried: 0
20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.
🏅 Sign in with Google to earn the 🕰️ Pendulum Timer badge when you pass — and a certificate when you finish all 10 lessons of Part 3 · Physics and STEM projects. You can still take the test without signing in.
Why does it work? When should you use it? Ask in English, मराठी or हिंदी.
Sign in with Google to ask Free — 20 questions a day.
Prefer a real teacher? TalentJR teachers take live online classes anywhere in India and visit homes in selected cities. Tell us what you need and our team will call you with timings and fees.