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Friction Basics question from NEET 2019

Q22NEET 2019Medium

Friction Basics

A body of mass mm is kept on a rough horizontal surface (coefficient of friction = μ\mu). A horizontal force is applied on the body, but it does not move. The resultant of normal reaction and the frictional force acting on the object is given by FF, where FF is,

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Answer: (d)

  1. Normal reaction N=mgN = mg; static friction f≤μmgf \le \mu mg.
  2. They are perpendicular, so ∣F⃗∣=N2+f2|\vec{F}| = \sqrt{N^2 + f^2}.
  3. ∣F⃗∣≤(mg)2+(μmg)2=mg1+μ2|\vec{F}| \le \sqrt{(mg)^2 + (\mu mg)^2} = mg\sqrt{1+\mu^2}
  4. So the answer is (d).
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