A 3.0kg block rests on a rough plane inclined at 25∘ to the horizontal. A horizontal force of 20N is applied to the block towards the plane so that it has a component acting up the slope. If the block is just about to slide up the plane, find the coefficient of static friction between the block and the plane. (Take g=9.8m s−2.)
a) 0.32
b) 0.28
c) 0.16
d) 0.47