Motion in a Plane

Physics · Class 11

Simulation · Physics · Class 11

Why constant speed still means acceleration

"Why constant speed still means acceleration" is a free, interactive Class 11 Physics simulation for NEET and JEE, built on the NCERT section "Uniform circular motion" in Motion in a Plane. A runner on a circle: velocity arrows at two nearby instants and their difference Δv point to the centre; |a| = v²/R; optional tangential acceleration tilts a off-centre. NEET has asked about this idea 2 times in 10 years of papers. JEE Main asked 40 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).

From the lesson Uniform circular motion in Motion in a Plane. Change the values and watch what happens.

Why constant speed still means accelerationPhysics · Class 11

What it shows

NCERT §3.10

A runner on a circle: velocity arrows at two nearby instants and their difference Δv point to the centre; |a| = v²/R; optional tangential acceleration tilts a off-centre.

Controls

4 to try

  • Sliderspeed v 1–10 m/s
  • Sliderradius R 5–40 m
  • SliderΔt 2 s → 0.05 s
  • Toggleconstant speed / speeding up

Try this

Set R and v so the centripetal acceleration is exactly 1.25 m/s², then switch on speeding-up and see a no longer points at the centre.

Common mistake

Constant speed means zero acceleration; centripetal acceleration is a constant vector.

In NEET

10 years of papers

Asked 2 times in 10 years of NEET.

See the past questions: Uniform Circular Motion, Motion in a Plane (chapter)

In JEE Main

42 shifts analysed

40 questions from Motion in a Plane across the 42 JEE Main shifts Lumi has analysed (2017–2026).

See the past questions

The idea behind it

NCERT §3.10

  • Uniform circular motion is motion on a circle at constant speed. The velocity is along the tangent and keeps changing direction, so the body is accelerated.
  • The acceleration points towards the centre (centripetal acceleration) and has magnitude a_c = v²/R.
  • a_c has constant magnitude but its direction keeps turning, always towards the centre, so it is not a constant vector; the constant-acceleration equations do not apply.
  • Angular speed ω = Δθ/Δt (rad/s); v = R ω and a_c = ω² R.
  • The time period T is the time for one revolution and the frequency ν = 1/T is revolutions per second; v = 2πRν, ω = 2πν and a_c = 4π²ν²R.
  • Jogging at 5.0 m/s on a circle of radius 20 m: ω = 0.25 rad/s, one lap takes 2π/0.25 ≈ 25 s, and a_c = 25/20 = 1.25 m/s² towards the centre.
  • If the speed is changing as well, the acceleration also has a component along the tangent and no longer points at the centre.

Questions

5 answers

What does the "Why constant speed still means acceleration" simulation show?
A runner on a circle: velocity arrows at two nearby instants and their difference Δv point to the centre; |a| = v²/R; optional tangential acceleration tilts a off-centre.
What mistake does the "Why constant speed still means acceleration" simulation fix?
A common mistake it clears up: constant speed means zero acceleration; centripetal acceleration is a constant vector.
Has NEET asked about this idea?
Yes. NEET has asked about this idea 2 times in 10 years of papers.
Does JEE Main ask questions from Motion in a Plane?
Yes. JEE Main asked 40 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 "Uniform circular motion" in Motion in a Plane (Class 11 Physics).

Embed this simulation

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