A block is moving on an inclined plane making an angle $45^{\circ}$ with the horizontal and the coefficient…
Solution


$ \begin{aligned} & F_1=m g \sin \theta+\mu m g \cos \theta \\ & F_2=m g \sin \theta-\mu m g \cos \theta \end{aligned} $ Given that, $F_1=3 F_2$ or $\left(\sin 45^{\circ}+\mu \cos 45^{\circ}\right)$ $ =3\left(\sin 45^{\circ}-\mu \cos 45^{\circ}\right) $ On solving, we get $\mu=0.5$ $ \therefore \quad N=10 \mu=5 $ $\therefore$ Answer is 5 . Analysis of Question Question is simple. Only one has to take care of direction and magnitude of friction. !
Asked in: JEE Advanced 2011 (Paper 1)