Monday, 7 November 2016

Centripetal, centrifugal force; differences, comparison and examples

Centripetal and centrifugal force

Are you a little bit confused about the differences between centripetal and centrifugal force?  Well then, carry on.

Centripetal Force

 It is defined as that inward force required to keep objects moving with a constant speed in a circular path.

 F = mv2/r
 V = rw
 = Mrw
    Where, "F" is the centripetal force, "m" is the mass of body, "v" is the velocity at
which the body is moving, "r" is the radius and "w" is angular velocity.

 The direction of a centripetal force of a body Is perpendicular to the direction of the velocity.

Type of force:    

 Centripetal Force keeps an object moving in its circular path, and prevents it from flying off.

When you tie a string to a stone, which is then whirled in a Circular path is suddenly cut, the stone files off the circular path.
 Centripetal Force was the force keeping the stone in its initial circular path.

centripetal and centrifugal force

Centrifugal force
 It is defined as that outward force required to keep it moving in circular path.

 It must be according to Newton’s third law of motion.

F = mv2/r

The direction of a centrifugal force of a body is equal and oppositely directed away from the center from which the body is moving. 

Type of force:      

centrifugal force is the inertia of motion.


Driving on a mud road and children feeling a force pushing them outwards.

Angular velocity (w)

     This is defined as the angle turned through divided by the elapsed time. Consider a stone whirled in a circular path. It move from the point A to B in T Seconds, so that the radius OA sweeps through the angle ɵ.

Angular velocity (w) = ɵ/t

Linear velocity (v) = s/t

Linear displacement (s) =

Where s is the length of arc AB, which is equal to linear displacement. If the angle ɵ is measured in radians.
The unit of radius is metre.
The unit of angular velocity is radians per second.
The unit of linear velocity is metre per second.
               360° = 2π = One revolution
               180° = π

     A stone whirled at the end of a road 30cm round, makes ten revolution in two seconds. Find:
a)     The angular velocity in radians per second.
b)     The  linear speed,
c)     The distance covered in 5 seconds.


  W = ɵ/t
   ɵ = 2π radian

   w = 20/2 = 10π rad/s

   w = (10 x 3.14) rad/s
   w = 31.4 rad/s

According to Ganse, “Centripetal force and centrifugal force are really the exact same force, just in opposite directions because they're experienced from different frames of reference.” 
Thanks for reading. 


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  1. Your statement on centripetal force is totally wrong. When a stone on a string is spun around in a circle, the force is outward on the string not inward to the centre. When the string is cut the stone will fly off in a STRAIGHT line, it will not ever follow the circle. This is easily proven on slow motion video.
    Centripetal force on Wikipedia uses and example of people on a rotor ride, which is also false. The force pushes the people outward, but the wall is the boundary that they are forced upon and they will not fall until the velocity slows down. They are NOT being pulled to the centre.
    This is a totally bogus theory.

  2. With all due respect, I would like for you to go back and do a proper study of centripetal force before you decide to correct. Please come back when you know better. Thanks for your comment.