The number of points, at which the function $f(x)=\max \left\{6 x, 2+3 x^2\right\}+|x-1| \cos \left|x^2-\frac{1}{4}\right|, x \in(-\pi, \pi)$, is not differentiable, is

$\_\_\_\_$ .

In a screw gauge when the circular scale is given five complete rotations it moves linearly by 2.5 mm . If the circular scale has 100 divisions, the least count of screw gauge is $\_\_\_\_$ mm.

The increase in the pressure required to decrease the volume ( $\Delta V$ ) of water is $6.3 \times 10^7 \mathrm{~N} / \mathrm{m}^2$. The percentage decrease in the volume is $\_\_\_\_$ .

(Bulk modulus of water $=2.1 \times 10^9 \mathrm{~N} / \mathrm{m}^2$.)

The time taken by a block of mass $m$ to slide down from the highest point to the lowest point on a rough inclined plane is $50 \%$ more compared to the time taken by the same block on identical inclined smooth plane. Both inclined planes are at $45^{\circ}$ with the horizontal. The coefficient of kinetic friction between the rough inclined surface and block is $\_\_\_\_$