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JEE Advanced 2012Paper 1
Exam
JEE Advanced
Year
2012
Paper
Paper 1
Subject
Physics
Chapter
Laws of Motion

JEE Advanced 2012 · Paper 1 · Physics · Laws of Motion

A small block of mass of 0.1 ~kg lies on a fixed inclined plane PQ...

A small block of mass of 0.1 kg0.1 \mathrm{~kg} lies on a fixed inclined plane PQ which makes an angle θ\theta with the horizontal. A horizontal force of 1 N1 \mathrm{~N} acts on the block through its centre of mass as shown in the figure. The block remains stationary if (take g=10 m/s2g=10 \mathrm{~m} / \mathrm{s}^{2} ) A small block of mass of 0.1 ~kg lies on a fixed inclined plane PQ which makes an angle θ with the horizontal. A

Options

  1. Aθ=45∘\theta=45^{\circ}
  2. Bθ>45∘\theta>45^{\circ} and a frictional force acts on the block towards P.
  3. Cθ>45∘\theta>45^{\circ} and a frictional force acts on the block towards Q.
  4. Dθ<45∘\theta < 45^{\circ} and a frictional force acts on the block towards Q.

Correct answer

A. θ=45∘\theta=45^{\circ}

Step-by-step solution

The various forces acting on the block are as shown in the figure. A small block of mass of 0.1 ~kg lies on a fixed inclined plane PQ which makes an angle θ with the horizontal. A
When θ=45∘,sin⁡θ=cos⁡θ\theta=45^{\circ}, \sin \theta=\cos \theta The block will remain stationary and the frictional force is zero. When θ>45∘,sin⁡θ>cos⁡θ\theta>45^{\circ}, \sin \theta>\cos \theta Therefore a frictional force acts towards QQ. When θ<45∘,cos⁡θ>sin⁡θ\theta < 45^{\circ}, \cos \theta>\sin \theta Therefore a frictional force acts towards PP.
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