Class 9 > Unit # 03: Dynamics > Uniform Circular Motion

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Unit No. 3 Dynamics - Centripetal and Centrifugal Force

Define Centripetal Force, its formula, and factors on which it depends:

Centripetal Force

"The force that causes an object to move along a curve (or a curved path) is called centripetal force."

Formula

$F_c = \frac{m v^2}{r}$

Where:
• $F_c$ = Centripetal Force
• $m$ = Mass of object
• $v$ = Velocity of object
• $r$ = Radius of the curved path

Factors on Which $F_c$ Depends

Centripetal force depends upon the following factors:

• Mass ($m$): An increase in the mass of the object increases the centripetal force ($F_c \propto m$).
• Velocity ($v$): It increases with the square of the velocity ($F_c \propto v^2$).
• Radius ($r$): It decreases with the increase in the radius of the curved path ($F_c \propto \frac{1}{r}$).

Q.10 Define Centrifugal Force and applications of centrifugal force:

Centrifugal Force

"A force supposed to act radially outward on a body moving in a curve is known as centrifugal force."

Explanation

Centrifugal force is actually a reaction to the centripetal force (according to Newton's Third Law). While centripetal force is directed towards the center of the circle, centrifugal force is directed away from the center of the circle or curved path.

Applications of Centrifugal Force

• Road Banking: The outer edge or bank of a curved road is raised to a certain height. This provides the necessary horizontal component of the normal force, supplying centripetal force to vehicle tires and preventing skidding.
• Cream Separator: Milk plants use high-speed spinners to separate cream from milk. Skimmed milk is heavier, while cream is lighter. When spun at high speed, heavy particles are pushed outward against the walls, driving lighter cream particles toward the center where they are collected through a tube.
• Washing Machine Dryer: Built-in dryers in modern washing machines spin wet clothes rapidly. Due to the circular motion, water droplets are thrown outward through the perforated walls of the dryer drum, drying the clothes instantly.

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