A 5 kg block is being held against the wall. What is the minimum force needed to keep the block from moving if the force is applied at an angle that is 15 degrees above the horizontal. The coefficient of static friction between the wall and the block is 0.275.

Answer 1

force = F

F sin 15 = F up

F cos 15 = F horizontal = F normal to wall

friction = mu F cos 15 up

total up= F sin 15 + .275 F cos 15

Fdown = m g = 5*9.81 = 49 Newtons

so
F (sin 15 + 0.275 cos 15) = 49