A block rests on a fixed rough inclined plane and a horizontal force $F$ is applied to it, as shown in the figure. Which of the following statements are correct?

(1) Normal reaction on the block is $F\sin \theta +mg\cos \theta$

(2) The frictional force is zero when $F\cos \theta =mg\sin \theta$

(3) The value of limiting friction is $\mu (mg\sin \theta +F\cos \theta )$

(4) The value of limiting friction is $\mu (mg\sin \theta -F\cos \theta )$

A brick of mass $2 \mathrm{kg}$ slides down an incline of height $5 \mathrm{m}$ and angle $30°.$ If the coefficient of friction of the incline is $\frac{1}{2\sqrt{3}},$ the velocity of the block at the bottom of the incline is (Assume the acceleration due to gravity is $10 \mathrm{m}/{\mathrm{s}}^2)$

A block of mass $5 \mathrm{kg}$ is kept against an accelerating wedge with a wedge angle of $45°$ to the horizontal. The co-efficient of friction between the block and the wedge is $\mu =0.4$. What is the minimum absolute value of the acceleration of the wedge to keep the block steady. Assume $g=10 \mathrm{m} {\mathrm{s}}^{-2}$