## Centripetal force:

“The force which is directed towards the centre of circle is called centripetal force.”

**Explanation:**

Consider a body moving with uniform speed in a circular path.In this case velocity changes only in direction and not in magnitude.Applying Newton’s first law of motion we find that some external force must be acting on the particle.Without presence of external force ,the velocity can’t change.Since velocity is changing continuously,therefore the external force must be acting continuously.

The direction of external force is such that only the direction of the velocity changes.This is possible only if the force always acts at right angles to the velocity.The direction of the velocity of the body is along the tangent to the circle at every point,so the external force must act at right angles to the tangents to circle at every point.Since radius and tangent are always perpendicular to each other,therefore the external force must acts along the radius of circle at every point.In other words ,the force is always directed towards the centre of the circle at every point.This point is called centripetal force.

### Centripetal force equation:

Consider an object of mass “m ” moving in a circle of radius “r” with constant speed “v” .The centripetal acceleration “ac” of the object is given as:

Since the direction of velocity of the body is changing continuously,therefore ,according to the first law of motion some force is acting on the body continuously.This force is known as centripetal force and is represented by “Fc”.

By Newton’s 2nd law of motion,magnitude of the centripetal force is given by:

### On which factors centripetal force depends?

- It depends on mass m of moving body.
- Square of its velocity.
- Reciprocal of the radius of the circle.

### Examples of centripetal force:

The moon revolves around the earth is the example of centripetal force.The gravitational force of the earth provides the necessary centripetal force.

### What are the applications of centripetal force?

There are some applications of centripetal force in our daily life which are given below:

- Banking of roads.
- Washing machine dryer.
- Cream separator.

**What dou mean by banking of roads?**

Raising outer edge of the roads is called banking of roads.

**Why the roads are banked?**

When a car takes a turn,centripetal force is needs to keep it in its curved track.The friction between the tyres and road provides the needed centripetal force.The car would skid if force of friction between tyres and the road is not enough particularly when roads are wet.This problem is solved by banking of curved roads.Banking of road means that outer edge of a road is raised.Imagine a vehicle provide the necessary centripetal force while taking a turn.Thus banking of roads prevents skidding of vehicles and makes driving safe.

**Washing machine dryer:**

The dryer of washing machine is basket spinner.It has a perforated wall having large number of fine holes in the cylindrical rotor.The lid of the container is closed after putting wet clothes in it.When it spins at high speed ,the water from wet clothes is forced out through these holes due to lack of centripetal force.

**What is Cream separator?**

Most modern plants use separator control the fact of various products.

**How do we separate cream from milk?**

A separator is a high speed spinner.It acts on the same principle of centrifuge machines.The bowl spins at very high speed causing the heavier contents of milk to move outward in the bowl pushing the lighter contents inward towards the spinning axis.Cream is lighter than other components in milk.Therefore ,skimmed milk which is denser than cream is collected at outer wall of the bowl.The lighter part of cream is pushed towards the centre from where it is collected through pipe.

## What is centrifugal force?

“The force which is directed away from the centre of the circle is called centrifugal force.” or

The reaction of centripetal force is called centrifugal force.

**Explanation:**

Consider a stone which is tied to a string moving in a circle.The necessary centripetal force acts on the stone through the string that keeps it to move in a circle.

According to Newton’s third law of motion,there exists a reaction of this centripetal force.Centripetal reaction that pulls the string outward is called centrifugal force.

### Difference table of centripetal vs centrifugal force:

Centripetal force | Centrifugal force |

1:It is the force which keeps the body to move in circle. | 1:It is the force which keeps the body away from circle. |

2:It is real force. | 2:It is a fictitious force. |

3:Its direction is towards the centre of circle. | 3:Its direction is away from the centre of circle. |

4:It is observed in inertial frame of reference. | 4:It is not observed in inertial frame of reference. |

**Video of centripetal vs centrifugal force:**