posted by Elise .
The rafters of a roof meet at an angle of 120 degrees. What force is exerted along the rafters by an object weighing 6000nt suspended from the peak?
Woulnt each rafer be supporting 3000N, so the compressive force is given by
cosine60 = 3000/compressive force
and solve for the compressive force. This gives you an idea why in past times flying buttresses were invented...to keep the walls from flying away.