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A block is placed on an rough inclined plane of inclination equal to the angle of repose. If it is moving up on incline with velocity v0 then its maximum displacement on incline will be -

Option: 1

\frac{v_{0}^{2}}{2g\sin \theta }


Option: 2

\frac{v_{0}^{2}}{4g\sin \theta }


Option: 3

\frac{v_{0}^{2}}{2g\cos \theta }


Option: 4

\frac{v_{0}^{2}}{4g\cos \theta }


Answers (1)

best_answer

Given-

\mathrm{\mu=tan\theta}

Initial velocity of block, \mathrm{u=v_{0}}

Let acceleration of block be a as shown in diagram below.

 

                             

 

                    \mathrm{ma=mg\ sin\theta+f_{k}}

                    \\ \mathrm{R=mgcos\theta}\\ \mathrm{f_{k}=\mu R=tan\theta \times mgcos\theta =mgsin\theta }

\\ \mathrm{ \Rightarrow ma=mg\ sin\theta+mg\ sin\theta}\\ \mathrm{ \Rightarrow a=2gsin\theta}

Let the maximum displacement up the incline be s. At the position of maximum displacement the velocity will be zero as the block is decelerated.

Using 3rd equation of motion-

\\ \mathrm{ v^2=u^2+2as}\\ \mathrm{ 0=v_{0}^2+2(-a)s}\\ \mathrm{s=\frac{v_{0}^2}{2a}=\frac{v_{0}^2}{4gsin\theta}}

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