Problem in Rigid Bodies

1. The problem statement, all variables and given/known data



The upper portion of the crane boom consists of the jib AB,

which is supported by the pin at A, the guy line BC, and the

backstay CD, each cable being separately attached to the

mast at C. If the 5-kN load is supported by the hoist line,

which passes over the pulley at B, determine the magnitude

of the resultant force the pin exerts on the jib at A for

equilibrium, the tension in the guy line BC, and the tension

T in the hoist line. Neglect the weight of the jib. The pulley

at B has a radius of 0.1 m.



2. Relevant equations



Rigid Bodies Equillibrium



3. The attempt at a solution



First of all, the problem seems to be BIG and contains lots of 'unnecessary' details. I am confused here in WHAT to take as my body to draw my FBD. Is it the jib AB or DAB... I followed my common sense and took AB.. Not only that but the JIB AB attached to the pulley as one system. Now, we ignore CD. I solved it and I got the correct answer by choosing moment about A by 3 different forces. Tension along BC along y axis and two tension around the pulley. (Even the horizontal tension has a distance from A)... NOW MY QUESTION STARTS!. The book gives one surprising FBD. It is included in the word document. One for the JIB and the other for the pulley. My question is WHY is there a 5 kN Horizontal and Vertical AT THE CENTER of the pulley. The forces are tangential.. How is it drawn inside? I suppose this is the reaction of the jib on the pulley. But HOW??... I am sorry for elongating the post. Thanks for bearing with me and being patient.

1. The problem statement, all variables and given/known data







2. Relevant equations







3. The attempt at a solution

Attached Files

FBD.docx (68.9 KB)