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?

1 answer

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.
http://www.google.com/images?q=flying+buttresses&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1219&bih=724