45
Q45. A block starts from rest from top of incline plane whose last $\frac{1}{3}$ rd part is rough. If block comes to rest at bottom, then value of coefficient of friction between block and incline plane is

                       
        $$\begin{gathered} \left(1\right) \mathrm{\mu } = \tan \mathrm{\theta } \\ \left(2\right) \mathrm{\mu } = \frac{1}{3} \tan \mathrm{\theta } \\ \left(3\right) \mathrm{\mu } =\frac{1}{2} \tan \mathrm{\theta } \\ \left(4\right) \mathrm{\mu } =3 \tan \mathrm{\theta } \end{gathered}$$