posted by Anonymous .
A worker stands still on a roof sloped at an angle of 23° above the horizontal. He is prevented from slipping by a static frictional force of 540 N. Find the mass of the worker.
m g sin 23 is the component of the worker's weight down the roof slope.
That equals the friction force 540 N
Solve M g sin23 = 540
to get the mass, M.
He's a pretty heavy guy, it seems.