ENGR 8
Assignment 9 Chapter 6.1-6.4
Due: next wed
Do problem 5 in Freemat/Matlab (include a FBD) and also problems 6 and 7 if you wish
Part I. Drills -- 1 point each
Part II. Assisted Problem Solving -- 2 points each
Plan: Use the Method of Sections
1) Draw the FBD
2) It is not necessary to determine reactions
at A and G
3) “Cut” the bridge members specified
4) Label Fcb, Fcf, Fef on the broken members
of the right section, keeping their original
direction
5) Set up the Eq of Equilibrium and solve
PLAN: Use Matlab
1) Draw FBD
2) In matlab start by setting W = 100 kN
3) Note that the block weight W provides a
vertical and horizontal force at D equal to
the block weight
4) Only 2 unknown forces at D means you can
set up equations and solve for Fde and Fdc
(positive means tension, negative compress)
5) continue solving all other members
6) when finished see which is violated, 30kN(T)
or 25kN(C) or both...which is the worse
violation in a proportional sense? Then scale
W by the ratio of limit to value. For example
if max T is 55, max C is 50, the worst violator
is C (2x limit). So W’ = W*25/50
(limit/value).
7) Plug in W’ back at start of solution and verify
8) Then calculate mass m = W/g
Part III. Unassisted Problem Solving -- 3 points each