Round a vertical circle
"Round a vertical circle" is a free, interactive Class 11 Physics simulation for NEET and JEE, built on the NCERT section "Conservation of mechanical energy" in Work, Energy and Power. A bob whirled in a vertical circle: speed and tension at every angle from energy conservation; below √(5gL) at the bottom the string goes slack before the top. NEET has asked about this idea 3 times in 10 years of papers. JEE Main asked 44 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Conservation of mechanical energy in Work, Energy and Power. Change the values and watch what happens.
What it shows
NCERT § Conservation of Mechanical Energy
A bob whirled in a vertical circle: speed and tension at every angle from energy conservation; below √(5gL) at the bottom the string goes slack before the top.
Controls
4 to try
- Sliderspeed at bottom 0–10 m/s
- Sliderstring length 0.5–2 m
- Slidermass 0.1–2 kg
- ReadoutT(θ), slack angle
Try this
Find the least speed at the bottom that just completes the loop (√(5gL)), and see where the string slackens at 0.9 of it.
Common mistake
Speed at the top can be zero; tension is largest at the top.
In NEET
10 years of papers
Asked 3 times in 10 years of NEET.
See the past questions: Uniform Circular Motion, Work-Energy Theorem, Work, Energy and Power (chapter)
In JEE Main
42 shifts analysed
44 questions from Work, Energy and Power across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "The Conservation of Mechanical Energy"
- If only conservative forces do work on a body, its total mechanical energy K + V stays constant.
- A body falling freely from height H has the same total energy mgH at every point: potential energy turns into kinetic energy as it falls.
- Speed at the bottom of a smooth curved track depends only on the height dropped, v = √(2gh), not on the shape of the track.
- For a bob whirled in a vertical circle on a string of length L, the minimum speed at the lowest point for completing the circle is √(5gL), and the minimum speed at the top is √(gL).
- When non-conservative forces like friction act, the loss in mechanical energy equals the work done against them: (K + V)_initial − (K + V)_final = work done against friction.
- The energy lost to friction is not destroyed; it appears mainly as heat, so total energy is still conserved.
Questions
5 answers
- What does the "Round a vertical circle" simulation show?
- A bob whirled in a vertical circle: speed and tension at every angle from energy conservation; below √(5gL) at the bottom the string goes slack before the top.
- What mistake does the "Round a vertical circle" simulation fix?
- A common mistake it clears up: speed at the top can be zero; tension is largest at the top.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 3 times in 10 years of papers.
- Does JEE Main ask questions from Work, Energy and Power?
- Yes. JEE Main asked 44 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Conservation of mechanical energy" in Work, Energy and Power (Class 11 Physics).
Embed this simulation
Free, with a link back
Teaching this idea? Put the simulation on your own page or LMS with this code.