Psyc 552 Ergonomics & Biomechanics Lecture 10

The Roger Problem – Weights  Body mass: 50 kg  Body weight: (50kg)(9.8m/s 2 )=490N  Load mass:10kg  Load weight: (10kg)(9.8m/s 2 ) = 98N  Weight of forearm – hand segment (50kg)(.022)(9.8m/s 2 ) = 10.78N  Weight of upper arm segment: (50kg)(.028)(9.8m/s 2 ) = 13.72N

The Roger Problem – Lengths Shoulder (0, 13) Elbow (2, 2) COM Hand (16, 4)

The Roger Problem – Lengths

 1 Square =.75”  SL FH = [ ] -1/2 = units – (14.14)(.75)(2.54cm)=26.9cm  SL UA = [ ] -1/2 = units – (11.18)(.75)(2.54cm)=21.3cm  COM FH =(26.9cm)(.682)=18.34cm  COM UA =(21.3cm)(.436)=9.29cm

The Roger Problem – Forces  R e = (98N x.5) N = 59.78N  M e = cos(8)[(26.9cm x 49N) + (18.34cm x 10.78N) = 1501 Ncm or Nm  R s = 59.78N N = 73.5N  M s = cos(280.3)[(21.3cm x 59.78N) + (9.29cm x 13.72N)] Ncm = 1751Ncm or 17.51Nm

Internal Forces

Low back models

Low back models (cont)

Lifting methods