Unit – II D |

## Concept of Centrifugal Force:

**Explanation :**

The magnitude of the centrifugal force is the same as centripetal force, but the direction is along the radius and directed away from the center of the circle. In vector form, the centrifugal force is given by- The force which is equal in magnitude but exactly opposite in direction to the centripetal force is called as centrifugal force. OR

The imaginary force which acts on the particle performing a circular motion in the direction away from the centre along the radius of the circular path having the same magnitude as that of centripetal force is called as centrifugal force.

- It should be noted that the centrifugal force is not real force’ since it does not arise due to either gravitational or electrostatic or nuclear interaction.

### Centrifugal Force is a Pseudo Force:

- Centrifugal force is not real force since it does not arise due to either gravitational or electrostatic or nuclear interaction.
- Centrifugal force has no independent existence. It comes to play with the action of the centripetal force.
- Centrifugal force acts in noninertial reference frame

Hence centripetal force is a pseudo force.

### Characteristics of Centrifugal Force:

- It is an imaginary force. Therefore it is called as a pseudo force.
- It is experienced in non – inertial frame of reference.
- It is always directed away from the center of the circle along the radius i.e. it is opposite to the centripetal force.
- Centrifugal force doesn’t have an independent existence.

### Examples of Centrifugal Force:

- When moving car along a horizontal curved road takes a turn, persons in the car experience a force in an outward direction. This force is centrifugal force.
- When the horizontal merry go round rotates about the vertical axis the chairs are pulled out due to centrifugal force.
- When a stone is whirled in a circle, we feel that stone is pulling our hand because of centrifugal force.
- The earth is flattened at the poles and bulged at the equator because the centrifugal force acting on the particles on the equator is maximum.
- The drier of washing machine acts on the principle of centrifugal force. Water particles from wet clothes are thrown outward due to centrifugal force acting on them.
- When a pilot moves the plane in looping a loop, he does not fall down because his weight is balanced by the centrifugal force acting on it.
- A coin kept slightly away from the center of rotating gramophone disc slips off towards the edge of the disc at a particular speed. This is due to centrifugal force acting on the coin.
- A bucket full of water is rotated in a vertical circle at a particular speed, so that water does not fall. This is because the weight of the water is balanced by centrifugal force.
- The centrifuge is a device which is used for separating heavier particles and light particles and works on the principle of centrifugal force. In centrifuge, the tube containing liquid along with the suspended particles is whirled in a horizontal circle. Dense particles are acted upon by centrifugal force. Hence they get accumulated at the bottom, which is outside while rotating. This is because buoyant force towards the center is greater for the lighter particle.

### Notes:

- Centripetal acceleration is also called as radial acceleration. It always acts along the radius towards the center of the circular path. The angle between radius vector and centripetal acceleration is π radian or 180°.
- Without centripetal force, circular motion is not possible. If centripetal force vanishes at some instant, then the body ceases to move in the circular path and flies along the tangent at that point to the circular path.
- The work done by the centripetal force is zero because the displacement of the particle (tangential) is perpendicular to the direction of the centripetal force (radial) i.e. there is no displacement in the direction of the centripetal force.
- Centripetal force is a real force while centrifugal force is pseudo force or imaginary force.
- Centrifugal force has no independent existence and it does not arise due to either gravitational or electrostatic or nuclear interaction.
- Centripetal force acts in inertial reference frame while the centrifugal force acts in the non-inertial reference frame.
- Centripetal force is a radial force, which acts along the radius and acts towards the center of the circular path.
- Centrifugal force has the same magnitude as a centripetal force but has opposite direction to it. i.e. centrifugal force acts radially outward.
- The torque produced by the centripetal force at the center of the circular path is zero.
- Kinetic energy of a body performing circular motion in terms of centripetal force is K.E. = F.r/2
- Linear momentum of a body performing circular motion in terms of centripetal force is p = F.r / v
- Change in velocity of a body performing U.C.M. and when it moves through angle θ is dv = 2 sin(θ/2)
- The direction of centripetal force does not depend on the sense of rotation of the body.
- On the surface of the earth, the centripetal force is maximum at the equator and zero on the poles.

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