ES226
STATICS
FALL 2010
PULLEYS AND FRAMES
Wednesday, Oct. 27th, 2010
LESSON OBJECTIVES
1. Compute the forces in pulleys, ropes, beam, and frame members that require multiple free-body diagrams.
2. Compute the reactions for compound beams, frames, or similar devices.
3. Show why it is advantageous to:
Cut and draw FBD’s of elements that have been separated at pin connections – remove pins and identify all the
elements of the system (you can draw a FBD of each element)
Identify 2-force members that occur in the frame structure
Pulley Example – Model – Not HW problem
In the real world
IN-CLASS PROBLEMS:
Determine the force P and the two cord forces needed
to support the 100-lb weight. Each pulley (numbered
“1”, “2”, and “3”) has a weight of 10 lb.
Determine the resultant forces at pins B and C on member
ABC of the four member frame.
2
Rope “R”
3
1
100 lb
The frame is pinned at A and E and also has pinned
connections between all bars at C B and D and F.
Determine the reaction forces at A and E and also at
all internal pin connections.
Assigned Homework:
Sections to Review in Textbook before next class:
Sections 6.6 – Understand Examples 6.9 – 6.21 in detail!
Due on Friday, October 29th
HW Problems – Solve the pulley problem on the backside
of this handout to turn in on Friday
Draw the system FBD and element FBDs (and think about what you can solve for with each FBD) for the problems on the
class handout (we did the first two in class) so do the other 8 and bring to class on Friday (don’t turn in yet)
ES226
STATICS
Problem 6-100
Solve for the forces in each cable and the force P required to hold the pulley system in equilibrium
if the weight is 100 lbs.
FALL 2010
ES226
STATICS
FALL 2010