**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° .

**Suggested solution**

On the point of motion
P = Wsin26° +
m Wcos26° < W

sin26° + m cos26° < 1

m cos26° < 1- sin26°

m <

tan l <

l <

l < 32°