Laws of Motion

JEE Main level, numerical answer, medium

167 of 210

Question 167 of 210

An inclined plane is bent in such a way that the vertical cross-section is given by y=x24y=\dfrac{{x}^{2}}{4} where yy is in vertical and xx in horizontal direction. If the upper surface of this curved plane is rough with coefficient of friction μ=0.5,\mu =0.5, the maximum height in cmcm at which a stationary block will not slip downward is________cm.cm.

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Answer: 25


At maximum ht. block will experience maximum friction force. Therefore if at this height slope of the tangent is
tan⁡θ,\tan \theta , then θ=\theta =Angle of repose
∴tan⁡θ=dydx=2x4=x2=0.5∴\tan \theta =\dfrac{dy}{dx}=\dfrac{2x}{4}=\dfrac{x}{2}=0.5
⇒x=1\Rightarrow x=1 and therefore y=x24=0.25my=\dfrac{{x}^{2}}{4}=0.25m
=25cm=25cm
∴∴ Answer is 25cm25cm
(Assuming that
xx & yy in the equation are given in meter)

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