BASIC BIOMECHANICS
8th Edition
ISBN: 9781259913877
Author: Hall
Publisher: RENT MCG
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Textbook Question
Chapter 13, Problem 9IP
A 10-kg block sits motionless on a table in spite of an applied horizontal force of 2 N. What are the magnitudes of the reaction force and friction force acting on the block? (Answer: R = 98.1 N, F = 2 N)
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Define the following parameters that can be assessed via isokinetic dynamometry (attempt to use your own words after reviewing data sheet):
Peak Torque
Time to peak torque
Angle of peak torque
Torque at 0.2 seconds
Peak torque/body weight
Total work
Work fatigue (Fatigue Index)
Average power
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.
A scientist was investigating if differences in the frictional work performed on a model car can change
depending on its mass (in grams) and whether the car moves up or down an inclined plane. They decided to
measure the amount of frictional force experienced by the model car and the distance it traveled in meters.
The scientists were able to evaluate the frictional work using the following data.
Mass (g)
Distance (m) Force
Work Done by Friction (J)
car going up the incline
100
39
0.063
2.457
car going down the incline 70
39
0.2309 ?
It is known that the relationship between force and distance determines the work done by friction (W+).
W₁ = fd
Wf work done by friction
f = force
d = distance
Question:
How much work done by friction was exerted on the car as it moved down the inclined plane?
You may use a calculator.
1
2.457
9.005
11.46
16.16
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Chapter 13 Solutions
BASIC BIOMECHANICS
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Ch. 13 - A 35-N hand and forearm are held at a 45 angle to...Ch. 13 - A hand exerts a force of 90 N on a scale at 32 cm...Ch. 13 - A patient rehabilitating a knee injury performs...Ch. 13 - A worker leans over and picks up a 90-N box at a...Ch. 13 - A man carries a 3 m, 32-N board over his shoulder....Ch. 13 - A therapist applies a lateral force of 80 N to the...Ch. 13 - Tendon forces Ta and Tb are exerted on the...
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