Who supplies the centripetal force?
"Who supplies the centripetal force?" is a free, interactive Class 11 Physics simulation for NEET and JEE, built on the NCERT section "Circular motion" in Laws of Motion. Three scenes—stone on a string, car on a level curve, rider in a rotor (death well)—with only real forces drawn; the inward net force is labelled as the centripetal force. NEET has asked about this idea 3 times in 10 years of papers. JEE Main asked 39 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Circular motion in Laws of Motion. Change the values and watch what happens.
What it shows
NCERT § Circular Motion
Three scenes—stone on a string, car on a level curve, rider in a rotor (death well)—with only real forces drawn; the inward net force is labelled as the centripetal force.
Controls
4 to try
- Togglescene string / level road / rotor
- Sliderspeed or ω
- Sliderradius 0.5–50 m
- Sliderμs 0.1–1.0
Try this
In the rotor (r = 2 m, μs = 0.5), find the least ω at which the floor can drop away and the rider stays put (ω = √(g/μr) ≈ 3.1 rad/s).
Common mistake
Adding 'centripetal force' as an extra arrow on the free-body diagram.
In NEET
10 years of papers
Asked 3 times in 10 years of NEET.
See the past questions: Uniform Circular Motion, Laws of Motion (chapter)
In JEE Main
42 shifts analysed
39 questions from Laws of Motion across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Circular Motion"
- Moving at speed v in a circle of radius R, a body has an acceleration v²/R directed towards the centre, so it needs a net force mv²/R towards the centre.
- Centripetal force is not a new kind of force; it is supplied by an existing force such as tension, gravity, or friction.
- On a level (unbanked) road the centripetal force comes only from static friction between tyres and road, giving a maximum safe speed v_max = √(μ_s R g), independent of the car's mass.
- Static friction, not kinetic, is used here because the tyres do not slip sideways on the road.
- On a road banked at angle θ, a component of the normal force also points towards the centre, raising the maximum safe speed.
- At the optimum speed v₀ = √(R g tan θ) the normal force alone supplies the centripetal force and friction is not needed, which reduces tyre wear.
- Below the optimum speed friction acts up the slope; above it, friction acts down the slope.
Questions
5 answers
- What does the "Who supplies the centripetal force?" simulation show?
- Three scenes—stone on a string, car on a level curve, rider in a rotor (death well)—with only real forces drawn; the inward net force is labelled as the centripetal force.
- What mistake does the "Who supplies the centripetal force?" simulation fix?
- A common mistake it clears up: adding 'centripetal force' as an extra arrow on the free-body diagram.
- 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 Laws of Motion?
- Yes. JEE Main asked 39 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 "Circular motion" in Laws of Motion (Class 11 Physics).
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