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T
T1
L
r
r
i
r
o
Case1
Case2
60
o
1cm
1cm
10cm
2 cm
Q
Q
(1/sec)
cP
0.1
1
1000
100
10
1
10
100
Viscosity
2000N
2000N
4000N
A
B
D
C
Stress
Strain
High Strain rate
Low Strain rate
η
K
o
K
1
800 N
5cm
2 cm
BIOM322 FINAL EXAM REVEW
1) Compare the bending moment acting on the spinal column at the level of a lumbar (lower
back) vertebra for a person carries books in a backpack.
There are 2 books:
the bigger book is 8
inches thick and weighs 4 lbs.
The smaller book is 2 inches thick and weighs 2 lb.
The books
can be stacked in the backpack with either book closest to the person’s back:
which book should
placed closest to the back to minimize the moment acting on the lumbar vertebra?
How much
less is the total moment for this placement versus the alternative placement? Discuss
quantitatively with proper free body diagrams.
2) A 250 lb. football player is tackled by 2 other players.
One pulls vertically down on the knee
with a force of 1500 N, and the other pulls vertically down on the calf with a force of 1000 N.
Assuming that the runner is on one leg at the time, compute the total force acting at the level of
the ankle, in a vertical direction.
Show a free body diagram that supports your answer.
3) Two shafts, as shown below are made of the same material and are of equal length and mass.
Let
r
i
= 1cm and r
o
= 3cm for Case 1.
Which shaft can support a larger twisting load before failure?
4)
An Achilles tendon is stretch by a unixial, tensile load of time time the body weight. The person’s bosdy
weight is 800N.
The cross sectional area of the tendon is 3cm
2.
The Young’s Modulus of the tendon is
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 Spring '08
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