Circular Motion: Centripetal & Centrifugal Forces

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Centripetal Force

The force that makes a body follow a curved path, i.e. maintain uniform circular motion

The direction of this force is always towards the centre of the circle

Vector quantity

Unit = newton

F = mω²r

F = centripetal force

m = mass of the body

ω = angular velocity

r = radius of rotation

F = mv²/r

F = centripetal force

m = mass of the body

v = linear velocity

r = radius

Examples of Centripetal Forces

Car turning a corner = friction

Planet orbiting the sun = gravity

Object twirling on a string = tension

All of these forces are centripetal and act towards the centre of the circular path

Without a centripetal force, circular motion does not occur

Centrifugal force

For every action there is an equal and opposite reaction, according to Newton's third law of motion

So, centripetal force must have an opposing force keeping the balance, making sure the object is maintained in circular motion

Centrifugal force balances out the centripetal force when an object is in circular motion

The direction of the centrifugal force is away from the centre of the circular path

Centrifugal force is the force that you feel when you are on a roller coaster, and if you weren't strapped in, this force would propel you from the seat.

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