Answer:
Force of Compression= 1,315.322 N
Shear Force = 0 N
Explanation:
Given
Mass of Box = 5kg
Mass of lower arm = 1.5kg
Mass of upper arm = 2kg
Mass of Torso = 27kg
Calculating the weight of the parameters above
Weight of Box = Wbox = 5kg * 10N/kg = 50N
Weight of Lower arm = Wlow = 1.5 * 10 = 15N
Weight of Upper arm = Wup = 2 * 10 = 20N
Weight of Torso = Wtor = 27 * 10 = 270N
The force on the muscle is calculated by the following:
Fmus= Wbox* a/5 + Wlow* b/5 + Wup*c/5 where a,b, and c represents the corresponding lengths of each weights
Calculating a,b and c (See attachment) where angles are 30° and 20°
a = (sin 30) * 14.2 + (cos 20) * 14.5
a = 7.1 + 13.6 = 20.7 in.
b = 13.6 + (7.1/2) = 17.2 in.
c = (14.5/2) cos 20 = 6.8 in
Fmus= 50 * 20.7/5+ 15* 2 * 17.2/5+ 20* 2 *6.8/5 = 364.3N
.... * 2.54 inch
Fmus = 364.3 * 2.54 = 925.322N
Force of compression is calculated as
Fcomp= Fmus + Wtor + Wbox+ 2* Wlow+ 2* Wup
Fcom = 925.322 + 270 + 50 + 2 * 15 + 2 * 20
Fcomp = 1,315.322 N
Fshear = 0 N because no force perpendicular to L5/S1
