Answer to Question #158311 in Classical Mechanics for nasia

Question

A beam LO weighing 50N rests against a wall, the lower part of the beam extending 15 m from the base of the wall. Calculate the minimum value of the force F that can be applied to keep the beam in equilibrium. The coefficient of friction at L and O is 0.30.

Answer 1

Answer

Consider that beam is making angle 45° with horizontal so

Moment about point O

$50\times7.5\times \sqrt{2}\times sin45+0.3N'\times\sqrt{2}cos45=N'\times15$

Therefore

N'=35.7Newton.

Force that requires to keep the beam in

equilibrium

$35.7\times0.3+Q=50cos45^°$

So

Q=24.6N