Friction and walking: Sand vs. concrete. Why is it more difficult to walk on a sandy surface than on a rigid concrete road under the same conditions? Choose the correct option.
IIT JEE
Physics
Difficulty: Easy
Choose an option
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ASand yields, reducing normal reaction and friction
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BConcrete has lower coefficient of friction
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CAir resistance is higher near sand
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DShoes become heavier on concrete
Answer
Correct Answer: Sand yields, reducing normal reaction and friction
Explanation
Concept
- Static friction ∝ normal reaction × coefficient of friction.
- On sand, the surface deforms and shifts, reducing effective normal reaction and reliable contact, so available friction is less.
Final AnswerSand yields, reducing normal reaction and friction