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

$A$ 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:

$A$ person initially at rest starts walking towards the east without slipping or skidding. What is the type of friction acting on the person from the ground, and in which direction does the frictional force act?

Calculate the maximum acceleration (in $m s^{-2}$) of a moving car so that a body lying on the floor of the car remains stationary. The coefficient of static friction between the body and the floor is $0.15$ $(g = 10 m s^{-2})$.

Static friction between two surfaces:

$A$ horizontal force just sufficient to move a body of mass $4 \,kg$ lying on a rough horizontal surface is applied on it. The coefficients of static and kinetic friction are $0.8$ and $0.6$ respectively. If the force continues to act even after the body has started moving, the acceleration of the body is (take $g=10 \,ms^{-2}$). (in $\,ms^{-2}$)