Which of the following forces does not depend on the velocity: the frictional force between the contact surfaces of two solids or the viscous force?

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?

$A$ pulling force $F$ making an angle $\theta$ with the horizontal is applied on a block of weight $W$ placed on a horizontal table. If the angle of friction is $\alpha$,then the magnitude of the force required to move the body is equal to

$A$ 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:

The maximum force of friction is called:

If the mass of an object is doubled,what will be the effect on the coefficient of friction?