This document discusses centripetal and centrifugal forces. It defines centripetal force as a real inward force that keeps an object moving in a curved circular path towards the center. Centrifugal force is defined as an apparent outward fictitious force felt by an object moving in a circular motion due to its inertia. Examples given of centripetal force include the moon orbiting the earth due to gravity, and a washing machine spinning clothes to remove water through centrifugal force. The key difference between the two forces is also summarized.

1. Centripetal and
Centrifugal Forces
MADE BY - ANKITA

2. Centripetal Forces
• Sir Isaac Newton explained it as “the force by which
objects are drawn, or in any way, towards a point as to
a center. In Newtonian mechanics, the force of gravity
provides the centripetal force for astronomical orbits. It
is a real force that is necessary to keep an object moving
in a curved path and that is directed inward toward the
centre of rotation , exerted on the body by the external
agencies like gravitational force, tension in the string
etc. It acts both in Inertial and Non –inertial frame.

3. CONT..
• The force needed by a body of mass m, to keep in a circular
motion at a distance R, from the centre of a circle with velocity v,
is the centripetal force Fc, where
• The direction of the force is towards the center of the circle of
motion, and its magnitude and direction can both be derived from
a consideration of Newton’s second law of motion

5. CONT..
• In astronomy many stars, planets and disks of material
move in circular orbits and require a force equivalent to the
centripetal force to maintain their circular motion. This force
is usually gravity. By balancing the gravitational and
centripetal forces it is possible to obtain estimates of the
mass within a given radius from the rotation curves
of galaxies or accretion disks around supermassive black
holes.

6. 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.
• Washing machine dryer: The dryer of the washing machine is basket
spinner. It has a perforated wall having a 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 a lack of centripetal force.

7. Centrifugal Forces
• Centrifugal force is the apparent outward force on a mass
when it is rotated. It is pseudo or fictitious force which
cannot arise from gravitational force, tension
etc. The centrifugal force is a pseudo-force because if the
centripetal force ceased for an object in circular motion, the
centrifugal force the body is “feeling” would instantly
disappear, and the object would travel tangentially to its line
of motion. It only arises because the body is in a non-inertial
frame of reference.

8. CONT.
• Centrifugal force is the apparent outward force on a mass
when it is rotated. Since Earth rotates around a fixed axis,
the direction of centrifugal force is always outward away
from the axis, opposite to the direction of gravity at
the equator; at Earth’s poles it is zero. (Centripetal force is
the necessary inward force that keeps the mass from moving
in a straight line; it is the same size as centrifugal force, with
the opposite sign. Centripetal force is real; centrifugal force
is just an apparent force.)

9. CONT..
• The reaction of the centripetal force is called the 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. The centripetal reaction
that pulls the string outward is called centrifugal force.

11. Centripetal Vs Centrifugal
•
Centripetal force Centrifugal force
1: It is the force which keeps the body to
move in the circle.
1: It is the force which keeps the body
away from the circle.
2: It is a real force 2: It is a fictitious force.
3: Its direction is towards the center of
the circle.
3: Its direction is away from the center of
the circle.
4: It is observed in the inertial frame of
reference.
4: It is not observed in the inertial frame
of reference.

12. THANK YOU