Key Concepts
• Centrifugal force
• Acceleration
• Angular acceleration
Introduction:
In this session we are going to study centrifugal force. We are going to differentiate between acceleration in rectilinear motion and uniform circular motion, and derive a relation to calculate the same.
Centrifugal force:
An outward force on a rotating or revolving body is called a centrifugal force. Centrifugal means “center-fleeing.” Centrifugal force does not pull an object outward. This is a misconception.

Newton’s First Law says that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force. It is not due to any real force rather due to inertia. The centrifugal force is not a true force as it is an effect of rotation. It is equal and opposite to the centripetal force

Acceleration:
It is defined as the rate of change of velocity.
Acceleration =
change in velocityTimechange in velocityTime
Acceleration exists when there is a change in velocity. Velocity is a vector quantity. It has both magnitude as well as direction associated with it.
If u is the initial velocity and v is the final velocity and t is the time taken then the formula is :
a =
v−utv−ut
This formula is used for linear motion, for the uniform circular motion we calculate the angular acceleration.
Centrifugal Acceleration:
It depends on the radius of the circle and the speed of the object.
It is denoted by “ac” Its unit is “m/s .”

Questions and answers
Question 1: Draw the direction of the centrifugal force if the object is released from its orbit at point 1 and 2.

Answer:
For object 1 it will go in horizontal direction towards the right.
For object 2 it will go vertically down.

Question 2: The speed of a boy of weight 40 Kg in a merry-go-round of radius 20 m is 40 m/s. What is the centrifugal force experienced by the system?
Answer:
Given that:
Speed of boy = 40 m/s
Radius of merry go round = 20 m
Mass of boy = 40 kg
Using formula,
FC=mv2r𝑭𝑪=𝒎𝒗𝟐𝒓
==
40
(40220)40220 =
40×40×402040×40×4020 = 3200 N
Question 3: What is the centripetal acceleration of an object if it going round in circles with velocity of 20 km/h and comes to rest in 20 s. The radius of the circle is 20 m.
Answer:
Given that:
Initial velocity,
u = 20 km/h = 20
×10003600 ×10003600
=
200 m/s36200 m/s36
Final velocity, v = 0 m/s
Radius, r = 20 m
Time period t = 20 s
aC=v2raC=v2r
=
(20036)2
××
120 =
200 ×20020 ×36 × 36 = 1.54 m/s2
Summary
- An outward force on a rotation or revolving body is called a Centrifugal force.
- It is pointed outwards.
- Centrifugal force is an inertial force.
Fc = Mv2/R
- Centrifugal acceleration depends upon velocity and radius.
ac=v2/r
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