TFS · Supporting topics · Problem 6PDFSolution in PDF ↓
TFS · Supporting topics · Problem 6
Problem & Solution
Video Synthesis
- Problem: A 5,000-pound machine rotates at 1800 rpm and is mounted on vibration isolators with a combined stiffness of 40,000-pound force per inch.
- Key values: 12 in
- Reference: reference handbook
- Result: And that equals 1,440 pound force, which is closest to answer choice D.
- ✅ Answer: D
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Student questions asked in live office hours about this problem
OH 97
Q: Where does the angular frequency formula with GC come from, and why isn't it in the handbook? I found ω = √(K/M) but the formula I need is ω = √(K·GC/M).
A: That GC factor is an unfortunate necessity in U.S. customary units due to the distinction between pound-force and pound-mass; in SI units the formula works directly without it. The handbook doesn't show it because it's a unit conversion artifact—when you work through the dimensional analysis in US customary units, you have to insert GC (32.2 lbm·ft/lbf·s²) to make the units cancel properly, unlike SI where everything naturally works out.