# Rizal 1

Topics: Weight, Force, Center of mass Pages: 2 (377 words) Published: August 28, 2013
Chapter FourName: _____________________
Due Wednesday, March 2, 2005

6.Explain why workstation designers should endeavor to have operators perform work elements without lifting their elbows.

7.What viewing distance would you recommend for a seated operator working at a computer terminal?

9.How may the basic motion “search” be eliminated from the work cycle?

10.What basic motion generally precedes “reach”?

11.What three variables affect the time for the basic motion “move”?

12.How does the analyst determine when the operator is performing the element “inspect”?

13.Explain the difference between avoidable and unavoidable delays.

14.Which of the 17 therbligs are classed as effective and usually cannot be removed from the work cycle?

15.Why should fixed locations be provided at the workstation for all tools and materials?

16.Which of the five classes of motions is used most by industrial workers?

Problems

6. A current problem in the U.S. Army is the neck/shoulder fatigue experienced by helicopter pilots. To be able to fly missions at night, the pilots wear night vision goggles, which are attached to the front of the helmet. Unfortunately, these are fairly heavy, causing a large downward torque of the head. This torque must be counteracted by the neck muscles, which then fatigue. To alleviate this problem, many pilots have started attaching random lead weights to the back of the helmet. Find the appropriate weight that would best balance the head and minimize neck fatigue. Assumptions:

(a) center of gravity (cg) of goggles is 8 inches in front of neck pivot point; (b) goggles weigh 2lbs.;
(c) max. volitional neck torque is 480 in lbs.;
(d) cg of lead weight is 5 inched behind neck pivot point, (e) bare helmet weighs 4 lbs.; and
(f) cg of helmet is 0.5 inches in front of neck pivot....