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JEE Main 2026 (28 Jan, Shift 1) · Friction on an Incline

Friction on an Incline question from JEE Main 2026 (28 Jan, Shift 1)

Q2JEE Main 2026 · 28 JAN · SHIFT 1Medium

Friction on an Incline

A block of mass 5 kg is moving on an inclined plane which makes an angle of 30∘30^\circ with the horizontal. Friction coefficient between the block and inclined plane surface is 32\frac{\sqrt{3}}{2}. The force to be applied on the block so that the block will move down without acceleration is ______ N. (g=10 m/s2).(g = 10\text{ m/s}^{2}).

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Answer: (b)

  1. Weight component down the slope: mgsin⁡30∘=50×0.5=25 Nmg\sin 30^\circ = 50 \times 0.5 = 25\text{ N}.
  2. Kinetic friction (up the slope while moving down): μmgcos⁡30∘=32×50×32=37.5 N\mu mg\cos 30^\circ = \dfrac{\sqrt{3}}{2} \times 50 \times \dfrac{\sqrt{3}}{2} = 37.5\text{ N}.
  3. Zero acceleration: F+25=37.5⇒F=12.5 NF + 25 = 37.5 \Rightarrow F = 12.5\text{ N} (down the incline).
  4. So the answer is (b) 12.5 N.
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