A body placed on a rough inclined plane just begins to slide, when the slope of the plane equal to 1 in 4. Calculate the coefficient of friction.
The slope of the plane equal to 1 in 4 implies that if BC = 1 and AB = 4. Suppose that the plane is inclined at angle $\theta$ with the horizontal AC. From the relation between the coefficient of friction and angle of repose, we have