Leaving Certificate 1999
Higher Level. Question 7 (a)
A particle of weight W rests on a rough plane inclined at 26° to the horizontal.
P is the least force, acting up along the plane needed to move the particle up the plane. Prove that if P is less than W then the angle of friction is less than 32° .
On the point of motion P = Wsin26° + m Wcos26° < W
sin26° + m cos26° < 1
m cos26° < 1- sin26°
tan l <
l < 32°