BASIC BIOMECHANICS
8th Edition
ISBN: 9781259913877
Author: Hall
Publisher: RENT MCG
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Textbook Question
Chapter 4, Problem 9IP
In Problem 8, how much total stress is present on the fifth lumbar vertebra if the individual holds a 222 N weight bar balanced across his shoulders? (Answer: 29.3 N/cm2)
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Explain the answer biomechanically
2. a) Label the system provided below, including the reference frame, moment arms and vector forces
with the information provided.
Internal moment arm = 4cm +0.04m
External moment arm relative
to the segment weight = 25cm 0.25m
External moment arm relative
to the load weight = 45cm 40.45m
Segment weight = 50 N
Load weight = 100 N
Lower leg segment angle relative
to horizontal plane = 45°
Quadriceps tendon angle = 45°
Axis of
rotation
MF
SW
LW
2b) Using the figure in 2a., calculate the external torque of the system relative to the normal
component of segment and load weights listed above.
2c) Calculate the amount of both the tangential component of the muscle force and the muscle force
itself required to keep this system in a state of static equilibrium.
With the shoulder flexed at 30°, the moment arm of the deltoid muscle is 2.0 cm. Solve
for the force exerted by the deltoid muscle at the glenohumeral joint give the following
assumptions:
The deltoid is the only active muscle at the glenohumeral joint
The weight of the humerus is 48 N.
The center of gravity of the humerus is located 30 cm from the shoulder center of
rotation
STATIC EQUILIBRIUM EQUATIONS
CONSIDERING ONLY THE DELTOID MUSCLE
Fo
MA =
18 Cn
COR
B=55".
0-30°
RaF 30 cm
FG = 24 N
Chapter 4 Solutions
BASIC BIOMECHANICS
Ch. 4 - Prob. 1IPCh. 4 - Prob. 2IPCh. 4 - Prob. 3IPCh. 4 - Prob. 4IPCh. 4 - Prob. 5IPCh. 4 - Prob. 6IPCh. 4 - What kinds of fractures are produced only by...Ch. 4 - Prob. 8IPCh. 4 - In Problem 8, how much total stress is present on...Ch. 4 - Why are men less prone than women to vertebral...
Ch. 4 - Hypothesize about the way or ways in which each of...Ch. 4 - Prob. 2APCh. 4 - Prob. 3APCh. 4 - Hypothesize as to the ability of bone to resist...Ch. 4 - How are the bones of birds and fish adapted for...Ch. 4 - Prob. 6APCh. 4 - Hypothesize as to why men are less prone to...Ch. 4 - Prob. 8APCh. 4 - How much compression is exerted on the radius at...Ch. 4 - If the anterior and posterior deltoids both insert...
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