MECH324 - Homework Hints, Answers, and Extra Requirements

Homework 9 (Chapter 11)


TO ENHANCE YOUR LEARNING, PLEASE TRY TO WORK THE PROBLEMS FIRST WITHOUT LOOKING AT THE HINTS AND ANSWERS BELOW.

MAKE SURE YOU SATISFY ALL REQUIREMENTS LISTED BELOW AND IN THE ORIGINAL PROBLEM STATEMENTS (UNLESS INDICATED OTHERWISE BELOW).

NOTE - BECAUSE MOST ANSWERS ARE PROVIDED, IT IS VERY IMPORTANT THAT YOU SHOW ALL STEPS IN YOUR WORK.  THE GRADING WILL BE BASED ON THE COMPLETENESS, CLARITY, AND CORRECTNESS OF YOUR WORK, NOT JUST THE ANSWERS YOU PROVIDE.



11-8
[100 pts]

  • Use 0.3 lbf/in3 for the specific weight of steel.
  • Show your work (e.g., include a printout from FOURBAR or MathCAD) for your complete kinematics analysis.
  • θ3=10.1°, Ω3=-41.6 rad/sec, α3=-336 rad/sec2
  • θ4=113°, Ω4=26.3 rad/sec, α4=2964 rad/sec2
  • For link 3, use: m3 = 0.038 slug, RCG3 = 3.977 in, ΔCG3 = 38.199°, IG3 = 0.467 slug in2. You are not required to show work for these quantities.
  • aG3x = -8636 in/sec2, aG3y = -12210 in/sec2
  • If using MathCAD (which is what I recommend), the most proper way to deal with units in matrix equation 11.9, is to divide each element in rows 3, 6, and 9 of the matrix equation (both sides) by your length unit (e.g., "in") because these rows represent torque equations that have different units (in-lbf) than the other equations which involve force (with units of lbf). Then, after solving the matrix equation, you would have to multiply the 9th element in your results vector by the same unit (in) to get the desired quantity (T12).
  • T12 = 23 ft lbf
  • Calculate the resultant force in each joint.
  • F12 = 58.0 lbf, F32 = 60.7 lbf, F43 = 105 lbf, F14 = 109 lbf