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Q88
(NDA-I/2024)
Science & Technology › Basic Science (Physics, Chemistry, Biology)
Official Key
Which one of the following about different frictional forces is correct ?
Explanation
The magnitude of frictional forces follows the order: Static friction > Kinetic friction > Rolling friction. This is based on the degree of interlocking between the surfaces in contact.
- Static Friction: This force acts when an object is at rest. It is the strongest because the microscopic irregularities of the two surfaces have enough time to interlock deeply, requiring significant force to initiate motion.
- Kinetic (Sliding) Friction: Once the object starts sliding, the contact points do not get sufficient time to interlock as firmly as they do at rest. Consequently, kinetic friction is always less than the maximum static friction.
- Rolling Friction: This is the weakest frictional force. When an object rolls, the area of contact is minimal, and there is no relative sliding at the point of contact. This is why it is easier to move heavy loads using wheels or rollers.
Thus, Option C correctly represents the decreasing order of these forces.
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