What can be inferred from the relation $f_S \leqslant \mu_S N$?

$A$ block of mass $M$ is placed on a rough surface with a coefficient of friction $\mu = 3$. If the applied force $F$ is $(4/5)$ of the minimum force required to just move the block,find the total force exerted by the ground on the block.

$A$ block of mass $m$ rests on a horizontal table with a coefficient of static friction $\mu$. What minimum force must be applied on the block to drag it on the table?

$A$ block of weight $W$ rests on a horizontal floor with coefficient of static friction $\mu$. It is desired to move the block by applying the minimum amount of force. The angle $\theta$ from the horizontal at which the force should be applied and the magnitude of the force $F$ are respectively:

Is it possible to jump off a perfectly smooth surface? Why?

$A$ block of mass $M$ is placed on a horizontal surface and it is tied with an inextensible string to a block of mass $m$,as shown in the figure. $A$ block of mass $m_0$ is also placed on $M$. If $\mu$ is the coefficient of friction between the block $M$ and the horizontal surface,then the minimum value of $m_0$ required to keep the block $m$ stationary is