Physics class 9th
Chapter No 03
Dynamics
Comprehensive Questions 11 and 12
Question. No 11
What is uniform circular motion? What are the factors on which magnitude of acceleration( centripetal acceleration) in uniform circular motion depends?
Answer
Uniform circular motion : the motion of a body in a circular path with uniform speed is called uniform circular motion.
Examples: 1) motion of the earth around the sun.
2) motion of an electron around the Nucleolus.
Centripetal acceleration: The acceleration of an object undergoing uniform circular motion is called centripetal acceleration.
Quantity: it is a vector quantity.
Symbol: it is denoted by ac with a small arrow over it .
SI unit : The SI unit of centripetal celeration is meter per second square ms*-2.
Mathematically: ac = v*2/r
Factors on which the magnitude of centripetal acceleration in uniform circular motion depends.
Centripetal acceleration depends upon the speed and and the radius of the circle. In case of uniforms circular motion the speed is constant then it depends upon the value of r (radius).
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Question No 12
What is centripetal force? Explain how centripetal force is used in banking of roads and centrifugation.
Centripetal force: The force that comples a body to move in a circular path is called centripetal force .
Quantity; it is a vector quantity.
Symbol: it is denoted by Fc with a small arrow Over it.
SI unit : the S A unit of centripetal force is Newton (N).
Mathematically:
Fc = - mv*2/r
The negative sign shows that it is always acting towards the center of the circle.
Applications of Centripetal Force:
1. Banking of Roads: Centripetal force plays a crucial role in the design of banked roads. When a vehicle takes a turn on a banked road, the centripetal force required to keep the vehicle moving in a curved path is provided by the friction force between the tires and the road surface. The angle of banking is carefully calculated to ensure that the required centripetal force is provided by the friction force, thereby preventing the vehicle from skidding or sliding off the road.
2. Centrifugation: Centripetal force is utilized in centrifuges, which are devices used for separating mixtures based on differences in density. In a centrifuge, a mixture is placed in a rotating container. The centripetal force exerted by the spinning container creates a strong outward force on the denser components of the mixture, causing them to move towards the outer wall of the container. This allows for the separation of different components of the mixture, such as in blood plasma separation or in the purification of chemicals.
3. Separator and Washing Machine Dryer: Centripetal force is also applied in the operation of separators, such as cream separators used in dairy industries. These machines separate cream from milk by spinning it rapidly, causing the denser milk to move towards the outer edges, while the lighter cream collects in the center. Similarly, washing machine dryers use the centripetal force to remove excess water from wet clothes. The spinning motion of the dryer drum creates the centripetal force, pushing the water towards the outer edges, allowing it to be extracted through drainage holes.
In summary, centripetal force finds practical applications in various fields, including road design, separation techniques, and household appliances. Understanding and properly utilizing centripetal force is crucial for achieving efficiency and safety in these applications.
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