Centripetal and Centrifugal Force: Differences, Examples and Solved Questions (ICSE Class 10)

Understand Centripetal and Centrifugal Force: Differences

Centripetal and Centrifugal Force: Differences: formulas and key facts

Equal size, opposite direction

$|{\vec{F}}_{\text{centrifugal}}|=|{\vec{F}}_{\text{centripetal}}|$

Centrifugal points away from the centre; centripetal towards it.

In the rotating frame

${\vec{F}}_{\text{real, inward}}+{\vec{F}}_{\text{centrifugal}}=0$

The rider feels at rest; only an observer in that frame adds the centrifugal force.

In the ground frame

${\vec{F}}_{\text{net}}={\vec{F}}_{\text{centripetal}}\ne 0$

The body is accelerating towards the centre; no outward force exists.

How to solve Centripetal and Centrifugal Force: Differences questions

1. 1Ground observer (or 'explain the motion'): name the real centripetal force and its agent; the body accelerates towards the centre.
2. 2Rider in the rotating system ('what does the passenger feel?'): describe an outward centrifugal force of the same size.
3. 3For directions: centripetal towards the centre, centrifugal away from it; velocity along the tangent.
4. 4For differences, give at least three: direction, real versus fictitious, agent or no agent (and frame).
5. 5For 'what happens when released', answer from the ground: along the tangent, not along the radius.

Centripetal and Centrifugal Force: Differences in real life

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Tricks to remember Centripetal and Centrifugal Force: Differences

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Petal seeks, fugal flees

  Centri-PETAL: centre-seeking (petere, to seek). Centri-FUGAL: centre-fleeing (fugere, to flee, as in 'fugitive').

  Use it when: Direction questions like 2025 Q2(i)(a).

• Real has a reason

  A real force always has an agent you can name. Centripetal: string, gravity, friction. Centrifugal: no agent, so not real.

  Use it when: Real versus fictitious.

• Inside feels, outside sees

  Only someone riding round feels centrifugal force; someone outside sees only the inward centripetal force.

  Use it when: Frame-of-reference questions.

• Not a pair, not a balance

  They do not act on different bodies, so they are not action-reaction; and the body is accelerating, so they do not balance.

  Use it when: Assertion-reason traps.

Centripetal and Centrifugal Force: Differences: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Where students lose marks in Centripetal and Centrifugal Force: Differences

The slips examiners see most often, and what to write instead.

• ✗Mistake: Centrifugal force towards the centre

  Centrifugal is 'centre-fleeing': it acts away from the centre.

  Wrong working

  Centrifugal force acts towards the centre.

  Right working

  Centrifugal force acts away from the centre.

  ✓Do this: Use 'petal seeks, fugal flees'.

  Usually costs: Reported for 2025 Q2(i)(a), where candidates confused it with centripetal force.

• ✗Mistake: Centrifugal force along the tangent

  The tangent is the direction of velocity; both forces act along the radius.

  Wrong working

  Centrifugal force acts along the tangential direction.

  Right working

  Along the radius, outwards.

  ✓Do this: Forces along the radius, velocity along the tangent.

  Usually costs: Reported for 2025 Q2(i)(a).

• ✗Mistake: Calling centrifugal force real

  It has no agent and appears only in the rotating frame.

  Wrong working

  Centrifugal force is the reaction of centripetal force.

  Right working

  Centrifugal force is an apparent force in the rotating frame; it is not a reaction force.

  ✓Do this: Ask: 'which body exerts it?' If none, it is fictitious.

  Usually costs: Difference and assertion-reason marks.

• ✗Mistake: Saying the forces balance in circular motion

  From the ground, the only radial force is centripetal, so the body accelerates.

  Wrong working

  Centripetal and centrifugal forces balance, so the body moves in a circle.

  Right working

  An unbalanced centripetal force makes the body accelerate towards the centre, so its path curves.

  ✓Do this: Explain motion from the ground unless the question asks what a rider feels.

  Usually costs: Reasoning marks.

Practice questions on Centripetal and Centrifugal Force: Differences

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which of these is a fictitious (apparent) force?
   (a) friction
   (b) tension
   (c) centrifugal force
   (d) gravitational force

   Hint

   Which one has no agent?

   Answer

   (c)

2. Q2 · 1 mark · Very short answerBoard level

   The centripetal force on a stone whirled in a horizontal circle is 8 N. State the size and direction of the centrifugal force that would be felt in the stone's rotating frame.

   Hint

   Same size, opposite direction.

   Answer

   8 N, away from the centre.

3. Q3 · 3 marks · Short answerHarder board level

   State whether true or false, with a reason: (a) The centrifugal force keeps the Moon in its orbit. (b) Centrifugal force appears only in a rotating frame. (c) Centripetal and centrifugal forces form an action-reaction pair.

   Hint

   Think about agents and about which body each force acts on.

   Answer

   (a) False: the Earth's gravitational pull (centripetal) keeps it in orbit. (b) True: it is an apparent force of the rotating frame. (c) False: an action-reaction pair acts on two different bodies; these are both described for the same body, and centrifugal force is not real.

4. Q4 · 2 marks · Short answerHarder board level

   A potter's wheel spins fast, and small blobs of wet clay fly off its rim. Explain this (a) as seen from the ground, (b) as the potter's assistant riding on the wheel might describe it.

   Hint

   What holds a blob to the wheel?

   Answer

   (a) The stickiness of the clay cannot supply enough centripetal force, so the blobs leave along tangents. (b) A centrifugal force throws the blobs outwards.

5. Q5 · 2 marks · Short answerHarder board level

   Draw a labelled diagram of a stone whirled in a horizontal circle. At one point show its velocity, the centripetal force on it, and the direction of the centrifugal force felt in its rotating frame.

   Hint

   Two arrows along the radius in opposite directions, one along the tangent.

   Answer

   Circle with centre O, stone at P. Velocity: along the tangent at P. Centripetal force: from P towards O (tension). Centrifugal force: from P away from O (labelled 'apparent, rotating frame only').

6. Q6 · 1 mark · Assertion-reasonHarder board level

   Assertion (A): A rider on a merry-go-round feels pushed outwards.
   Reason (R): The merry-go-round exerts a real outward force on the rider.
   (a) Both true and R explains A (b) Both true, R does not explain A (c) A true, R false (d) A false, R true

   Hint

   Which way does the merry-go-round actually push the rider?

   Answer

   (c). The merry-go-round pushes the rider inwards; the outward push is an apparent centrifugal force.

7. Q7 · 3 marks · Short answerHOTS / competency

   A stone is whirled on a string that can stand a pull of 6 N. At the present speed the centripetal force needed is 5 N. The speed is slowly increased until the string breaks. (a) Why does it break? (b) In which direction does the stone then move? (c) Why would 'the centrifugal force pulls it outwards' give a wrong prediction of the path?

   Hint

   Faster motion on the same circle needs a larger inward pull.

   Answer

   (a) At higher speed the centripetal force needed exceeds 6 N, more than the string can supply. (b) Along the tangent at the point of breaking. (c) A real outward force would send it along the radius, but it actually goes along the tangent: no outward force acts in the ground frame.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Direction of centrifugal force?Show answer

   Along the radius, away from the centre.

2. 2.Is centrifugal force real?Show answer

   No, it is fictitious (apparent), felt only in a rotating frame.

3. 3.Centripetal force is 3 N. Size of centrifugal force?Show answer

   3 N (opposite direction).

4. 4.Who supplies the centripetal force on a car turning on a level road?Show answer

   Friction between the tyres and the road.

5. 5.Are centripetal and centrifugal forces an action-reaction pair?Show answer

   No.

Centripetal and Centrifugal Force: Differences: frequently asked questions