In the figure shown,a horizontal force $F_1$ is applied on a block,but the block does not slide. Then,as the magnitude of the vertical force $F_2$ is increased from zero,the block begins to slide. Which of the following statements is correct?

$A$ block of mass $2 \, kg$ is placed on a surface with a coefficient of friction $\mu = 0.4$. If a force of $2.5 \, N$ is applied to it,the frictional force will be ........ $N$.

As shown in the figure,a block of mass $\sqrt{3} \text{ kg}$ is kept on a horizontal rough surface with a coefficient of friction $\mu = \frac{1}{3 \sqrt{3}}$. $A$ force $F$ is applied on the vertical face of the block at an angle of $60^{\circ}$ with the horizontal. The minimum force $F$ required to just move the block is $3x$. Find the value of $3x$.
$\left[ g = 10 \text{ m/s}^2; \sin 60^{\circ} = \frac{\sqrt{3}}{2}; \cos 60^{\circ} = \frac{1}{2} \right]$

$A$ wooden block of mass $M$ lies on a rough floor. Another wooden block of the same mass is hanging from the point $O$ through strings as shown in the figure. To achieve equilibrium,the coefficient of static friction between the block on the floor and the floor itself is:

$A$ body of weight $50 \,N$ is placed on a horizontal surface as shown in the figure. The minimum force required to move the body is $28.28 \,N$. The frictional force and the normal reaction are respectively.

The coefficient of friction $\mu$ and the angle of friction $\lambda$ are related as