BASIC BIOMECHANICS
8th Edition
ISBN: 9781259913877
Author: Hall
Publisher: RENT MCG
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Chapter 3, Problem 3AP
A football player is contacted by two tacklers simultaneously. Tackler A exerts a force of 400 N, and tackler B exerts a force of 375 N. If the forces are coplanar and directed perpendicular to each other, what is the magnitude and direction of the resultant force acting on the player? (Answer 548 N at an angle of 43° to the line of action of tackler A)
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A) Describe the difference between strength and power during a squat. Provide a quantitative example that illustrates the difference.
B) During a squat, the weight you have on your shoulders has a certain amount of gravitational potential energy. As you squat down and come to a stop at the bottom of the squat, some of that energy is lost. Where does it go?
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.
The adjacent diagram displays the joint reaction force between the acetabulum and femoral head for the right leg during single leg stance. Also shown are the abductor muscle force (AMF), the weight of the body above the level of the stance hip (W) and their corresponding moment arms with respect to the joint centre (D and D1). If the right leg weighs 1/6 of total body weight, the ratio of D1 to D is 2.4, and AMF is angled at 30 degrees relative to the vertical, calculate the:
Abductor muscle force (2 marks).
Hip joint reaction force (2 marks).
Express both answers as multiples of total body weight
Chapter 3 Solutions
BASIC BIOMECHANICS
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